'He's in big trouble': Vulnerable GOP senator tempts fate as he backs Trump's cover-up

Former Missouri Democratic Sen. Claire McCaskill warned on Wednesday that Republican Sen. Cory Gardner of Colorado is risking his seat by complying with the GOP plan to limit President Donald Trump's impeachment trial.

With the initial stages of the trial coming to a close, senators will soon face a choice of whether to bring witnesses into the trial or to move toward a final vote on Trump's removal. Democrats have been urging for lawmakers to bring in witnesses, including, most prominently, former National Security Adviser John Bolton to fill out the factual record, a plan most Americans approve of. Most Republicans, however, are eager to get the trial over with and fear that bringing forward more witnesses might only make their goal of acquitting Trump harder.

So attention has turned to the key Republican senators believed to be most likely to split with the president's interest, including Sens. Lisa Murkowski of Alaska, Susan Collins of Maine, and Mitt Romney of Utah. And on Wednesday, a key Republican from a swing state — Sen. Cory Gardner of Colorado — announced that he is opposed to bringing forward more witnesses, including Bolton.

“I do not believe we need to hear from an 18th witness," Gardner said in a statement to Colorado Politics. "I have approached every aspect of this grave constitutional duty with the respect and attention required by law, and have reached this decision after carefully weighing the House managers and defense arguments and closely reviewing the evidence from the House, which included well over 100 hours of testimony from 17 witnesses.”

The Wall Street Journal had previously reported that at a meeting of Republican senators Tuesday night, Gardner expressed concern that a "longer trial would lead to more Democratic attacks."

McCaskill, in response to Gardner's comments, indicated that she thought his choice would backfire.

"Wow wow oh wow," she said in a tweet. "He’s in big trouble."

She added: "For everyone who does 'Most Vulnerable [Incumbent] Senators' lists.... this should rocket him to the top."

Gardner has long been on the shortlist of Republican senators that Democrats hope to replace in 2020. In 2016, Hillary Clinton won the state by almost five points.

And Gardner's standing in his state looks particularly weak. Morning Consult polls show he's three points underwater, with 37 percent approval and 40 percent disapproval. This isn't terrible — it means a substantial portion of the state has no opinion of him either way. But Trump himself is toxic in the state — 39 percent approve of the president, while 57 percent disapprove. That suggests anything Gardner does that pull him closer to Trump will likely hurt him in the general election.

But he also knows he can't vote to remove the president without completely undercutting his own support from Republican voters, as well as perhaps the national party. So he appears to be trying to make his eventual vote to acquit Trump as painless as possible, and that means getting the trial over quickly.

If McCaskill is right, though, his purpose could backfire. Trying to stop witnesses from testifying will likely be seen as aiding in Trump's cover-up, and that could push Colorado voters even further away.