How to make lines for political party charts | Adobe Illustrator Tutorial

Lehan Edirisinghe and Elle Trump July 21, 2025

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Key takeaways

  • Political-party crossover lines are easier to control when built from separate geometric shapes rather than continuous curves. The creator uses rectangles and quarter-circle segments because stretching conventional curved paths in Adobe Illustrator can cause unwanted distortion.

“I like to do a lot of things in Illustrator in pieces. It just gives you more control.”

  • A perfectly matched curve begins with two concentric circles and Illustrator’s Minus Back tool. The outer circle spans the two party lines, while the inner circle matches their gap; placing the smaller circle behind the larger one and applying Pathfinder → Minus Back creates a ring with the correct line thickness.

  • Two additional Minus Back operations turn the ring into a reusable quarter-circle. The creator places rectangles behind successive halves of the ring and subtracts them, then uses the Eyedropper tool to match the resulting segment to the party's color.

  • Two rotated quarter-circle segments joined by rectangular bars create a complete curved transition. The creator duplicates the first segment, rotates it into position, and adjusts the straight sections until they form a smooth-looking line without joining the individual objects.

  • The opposing party's crossover is created by copying, recoloring, and reflecting the completed construction. Using Transform → Reflect → Vertical produces the opposite movement, allowing one party's line to rise while the other falls without rebuilding the curves.

  • A slight horizontal offset keeps both parties visible where their lines cross. The creator deliberately shifts the advancing party's line so it does not completely obscure the declining party's line, improving the chart's readability.

  • Rapid party switches can be illustrated by horizontally compressing the crossover. This makes changes appear closer together on the timeline, although excessive compression distorts the curves and produces an unattractive result.

All points

29 gathered points · 1108 words

  • The tutorial explains how to create political-party crossover lines for historical timelines. The creator uses these charts to show changes in political-party positions, including moments when one party overtakes another. Viewers on the channel’s subreddit had asked how to reproduce the charts for other countries.

  • Adobe Illustrator is the software used, but the method should also work in LibreOffice. The creator demonstrates the underlying construction technique rather than software-specific instructions for every step. LibreOffice users would need to adapt the commands to its available tools.

  • Each curved line is built from independent geometric shapes. Instead of drawing one continuous curved path, the creator combines rectangles and quarter-circle segments. This gives greater control over the appearance and positioning of individual parts.

  • Separate shapes help avoid unwanted distortion when editing curves. Illustrator can produce unexpected results when certain curved lines are stretched or resized. Constructing curves from independent pieces makes adjustments more predictable.

  • The demonstration begins with two horizontal lines representing competing political parties. A red line and a blue line initially run parallel before changing positions. The goal is to create a smooth crossover in which the blue party overtakes the red party.

  • The first step is drawing a large circle that spans the combined height of the two lines. Illustrator's ellipse tool creates the shape, while holding Shift maintains a perfect circle rather than an oval. The circle's diameter must match the intended vertical distance across the crossover.

  • A smaller circle determines the inside boundary of the curved line. The second circle is sized to fit the vertical gap between the two horizontal bars. Together, the two circles establish the thickness of the curved segment.

  • The two circles must be aligned before cutting. The smaller circle is positioned inside the larger circle so that removing it creates a ring with a consistent width. That width must match the thickness of the original horizontal lines.

  • Illustrator's Pathfinder panel contains the Minus Back tool used to construct the curve. The creator highlights Minus Back as an underrated feature that he frequently uses. The same panel contains other shape operations, including Unite and Divide.

  • Minus Back removes the rear object from the object in front. The smaller circle must first be placed behind the larger circle using the right-click menu's Arrange → Send to Back command. Selecting both objects and applying Minus Back cuts a circular hole, producing a doughnut-shaped ring.

  • The order of overlapping objects is essential to the subtraction operation. During the demonstration, the creator initially attempts Minus Back before arranging the smaller circle correctly. He corrects the mistake by sending the smaller circle behind the larger one and repeating the operation.

  • The resulting ring has the same thickness as the horizontal party lines. Because the circles were sized according to the original bars and their spacing, the ring can connect to the straight sections without changing line thickness.

  • The complete ring must be reduced to a quarter-circle segment. Although Illustrator's Scissors tool could accomplish this, the creator demonstrates how to perform the operation with Minus Back.

  • The first cut removes half the ring. A rectangle is placed behind one half of the doughnut. Selecting the rectangle and ring and applying Minus Back removes the covered half, leaving a semicircular segment.

  • The second cut produces a quarter-circle. Another rectangle is positioned behind half of the remaining semicircle. Repeating Minus Back removes that section, leaving one quarter of the original ring.

  • The Eyedropper tool quickly matches the curve to an existing party color. The creator selects the quarter-circle, activates the Eyedropper, and samples the red horizontal line. The curved segment immediately adopts the same red appearance.

  • The quarter-circle is rotated to create the first downward bend. The creator demonstrates rotating a selected shape by moving the pointer near its corner and dragging, while using Shift. He positions the segment where the red line begins descending.

  • The straight-line section is shortened to meet the curved segment. Rather than allowing the original rectangle to extend beyond the bend, the creator adjusts its length until the pieces connect cleanly.

  • A second quarter-circle completes the transition back to a horizontal line. The first curved segment is duplicated using Command+C and Command+V on a Mac. The duplicate is rotated and positioned to create the second bend.

  • A copied straight rectangle completes the red crossover line. Once the two quarter-circle segments are positioned, another horizontal section is duplicated and connected to them. The resulting shape consists of multiple independent objects but visually appears to be one continuous line.

  • The blue crossover can be created by duplicating the completed red construction. Instead of rebuilding the curves, the creator selects and copies the entire red arrangement. This preserves the geometry and dimensions of the original.

  • The Eyedropper changes the duplicated construction from red to blue. Sampling the existing blue line applies its appearance to the copied shapes, ensuring consistent coloring across the chart.

  • Illustrator's Reflect command reverses the crossover direction. With the blue construction selected, the creator uses Transform → Reflect → Vertical. This mirrors the arrangement so that the blue party can rise while the red party falls.

  • The mirrored blue construction is positioned over the red one to create the crossover. Both arrangements use matching curved segments and straight sections, allowing the party lines to exchange vertical positions.

  • A slight horizontal offset improves visibility where the lines cross. The creator deliberately shifts the line representing the party moving ahead so that part of the declining party's line remains visible. Without this adjustment, one line can obscure too much of the other.

  • The same construction can represent multiple party switches. By copying, recoloring, reflecting, and repositioning the existing curved sections, the creator demonstrates how another crossover can be added without rebuilding the geometry.

  • Rapid changes in party positions can be represented by horizontally compressing the crossover. When two political parties exchange positions within a short period, the creator sometimes selects the entire crossover area and reduces its width.

  • Excessive compression makes the crossover visually unattractive. The creator notes that shortening the construction works reasonably well up to a point, but extremely narrow curves begin to look distorted. The amount of compression therefore depends on the available space and how quickly the parties switch positions.

  • The method prioritizes visual control over constructing a single continuous path. The completed timeline curves remain collections of rectangles and quarter-circle segments. Their modular structure allows the creator to adjust line lengths, colors, directions, crossing positions, and spacing independently while maintaining a consistent appearance.