Rhode Island Gov. Lincoln Chafee is switching parties to become a Democrat. Why is this happening? Because President Obama is enjoying decent approval ratings, and Rhode Island is a Democratic state. The Atlantic Wire plotted the timing of politicians' party switching along the president's approval rating, and we found that presidential approval serves as a pretty good guide for when these guys will switch. 

This is Chafee's second switch, having left the Republican Party in 2007, several months after losing his Senate seat — and when George W. Bush's approval ratings were slipping. In 2010, amid the Tea Party wave, Chafee won a three-way race as an Independent, getting 36 percent of the vote, compared to the Republican candidate's  33.5 percent and the Democrat's 23 percent. But Rhode Island voted for President Obama by 27 points in 2012. Obama's approval ratings have held, despite a trio of scandals. Chafee's up for reelection in 2014, so his switch looks necessary for political survival. Just like it was for the many backstabbers tho preceded him. Switchers like Bob Smith, the New Hampshire senator who switched from Republican to Independent in 1999 to run for president, and then switched back to Republican a few months later — after Chafee's father, Sen. John Chafee, died, so Smith could get Chafee's sweet committee chairmanship.

How to read this chart: We graphed each party switch since President Clinton's first term. Each light gray horizontal line marks a different month between 1993 and 2013. The jagged line running down the middle indicates presidential approval (solid) and disapproval (dashed) ratings as tracked by Gallup. The scale is from zero percent at left to 50 percent (the solid grey vertical line) to 100 percent at right. The color of the approval line changes with each presidency: Clinton and Obama in blue, Bush in red.

Each party changer is then identified in a box including his title, name, home state, and the switch that he made. The arrow on the box points to the month during which it happened.