Independent Rep. Justin Amash (MI-03), who defected from the GOP in July and voted for both articles of impeachment, said in November that he still plans to run for reelection. But Michigan's filing deadline for third parties isn't until July and the former Tea Party poster child could either continue running an uphill reelection bid in a three way race, seek the Libertarian nod for president or not run for anything at all.

The situation in Grand Rapids is unique, but Amash's impeachment stance (and the fact Democratic freshmen are even lobbying for him to serve as a manager in a Senate trial) complicates Democrats' math. Any path in 2020 probably involved Amash siphoning votes from the GOP nominee, reducing the threshold for victory. Now, Amash's anti-Trump posture seems more likely to split votes on the left.

Unlike pro-Trump party switcher Rep. Jeff Van Drew (NJ-02), Amash is now his own island. It's doubtful there's a sufficient market for a pro-life/pro-impeachment independent in the district to allow him a path to a sixth term. He had $273,000 in the bank at the end of September - far less than the GOP nominee is likely to be able to spend — and won't be able to lean on financial support from either party.

In 2016, President Trump carried this district 52 percent to 42 percent, and although parts of the Grand Rapids area are growing more prosperous and open to voting for Democrats, other parts —such as Battle Creek, where Trump just held a rally - are getting more Trump-friendly. In 2018, when Amash was still in the GOP fold, he beat a weak Democrat 54 percent to 43 percent.

The August GOP primary is a genuinely competitive affair between DeltaPlex arena owner Joel Langlois, state Rep. Lynn Afendoulis, and Iraq/Afghan War veteran and grocery empire heir Peter Meijer. Meanwhile, the frontrunner for the Democratic nomination is immigration attorney Hillary Scholten, who had $165,000 on hand to former Obama aide Nick Colvin's $136,000 at the end of September.

Either way, the math is tough for Democrats. As long as Amash stays in, he could split the anti-Trump vote, which is still likely to constitute a minority of voters in 2020. But if Amash doesn't seek reelection, Democrats could end up facing a self-funder (Langlois or Meijer) in a seat Trump carried by nearly ten points in 2016. For now, this seat moves from Toss Up to the Lean Republican column.