The conventional wisdom is that a divided Senate means impeaching Trump is next to impossible. I’m not so sure. I believe there is some risk to Trump, and that things could turn against him rapidly.
If all Democratic Senators vote for conviction, they would only need to flip 20 Republican Senators to reach the 2/3 majority needed to convict.
Most Republicans recognize Trump is a blowhard and loose cannon. They would much prefer to go into the 2020 election united by Mike Pence, someone they consider more stable and electable.
The problem is that while most Republicans Senators despise Trump, they are afraid of him, or more accurately, Trump’s base. If there were an anonymous vote, Trump would be convicted.
As noted by Politico, an anonymous vote is a possibility. A bare majority of the Senate can set the rules. If this were to happen, getting the needed 20 Republican votes begins to look very possible. As Politico explained:
[I]t’s not hard to imagine three senators supporting a secret ballot. Five sitting Republican senators have already announced their retirements; four of those are in their mid-70s or older and will never run for office again. They might well be willing to demand secrecy in order to give cover to their colleagues who would like to convict Trump but are afraid to do so because of politics in their home districts. There are also 10 Republicans senators who aren’t up for reelection until 2024 and who might figure Trumpism will be irrelevant by then. Senators Mitt Romney and Lisa Murkowski have been the most vocal Republicans in expressing concerns about Trump’s behavior toward Ukraine.Politico
More good news for the Democrats: Monolithic support for Trump is less likely in the Senate. House district boundaries can be drawn to make seats “safe” for a Republican. Senators are more vulnerable, because it’s harder to gerrymander a state. Senators have less reason to be afraid of Trump’s base, which remains a minority of the country as a whole.
As Politico concludes:
A secret ballot might get Trump out of office sooner than everyone expects: The sooner any three Republican senators make clear that they will support nothing short of a secret ballot, the sooner Trump realizes his best course could be to cut a deal, trading his office for a get-out-of-jail-free card—a clean slate from prosecutors—just as Vice President Spiro Agnew did. And if Trump were to leave office before the end of the year, there might even be enough time for Republicans to have a vibrant primary fight, resulting in a principled Republican as the nominee.
All in all, Trump may be more vulnerable than he initially appears.