Senate Majority Leader Mitch McConnell, R-Ky., may have successfully corralled his Republican colleagues Tuesday to defeat 11 efforts by Senate Democrats to subpoena key Trump administration witnesses and documents (and modify other rules) in the Senate impeachment trial. But these tactics have likely put Republican senators facing competitive races in an impossible bind; two January polls show that, in both battleground states and swing counties, more voters support Trump’s removal than approve of him. That dynamic could cost the Republicans control of the Senate after the 2020 elections — and, in that event, McConnell’s powerful post as majority leader will also be forfeited.

McConnell successfully tabled 10 of 11 Democrat-offered amendments by a party line vote of 53-47 (Sen. Susan Collins, R-Maine, sided with the Democrats on the eleventh), most of which sought to subpoena key Trump administration witnesses and documents to be evidence in the Senate trial. But the collateral damage could be grave.

Because of McConnell’s strong-arming, every Republican senator is now on the record opposing subpoenas requiring former national security adviser John Bolton, Office of Management and Budget head Mick Mulvaney, Secretary of State Mike Pompeo and other administration officials to testify. These votes will be fodder for Democratic campaign ads against vulnerable Republican senators who are standing for re-election this year — particularly in Maine, Colorado and Arizona. (Remember that 71 percent of Americans in a December poll by The Washington Post/ABC News thought Trump should allow his aides to testify.)

Some of these senators have left open the possibility that they may support calling witnesses if, after the House managers and the president’s lawyers complete their separate presentations, the Republicans’ expected motion to dismiss the articles of impeachment is defeated.

That may well be a hollow gesture because it is hardly a foregone conclusion that a motion to dismiss the articles will be defeated. If the Senate does dismiss the impeachment charges without hearing witnesses or completing the trial, the “see no evil, hear no evil” attitude of Republican senators will clearly clash with most Americans’ sense of what constitutes a fair trial.

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If, however, Sens. Mitt Romney, R-Utah, and Lisa Murkowski, R-Alaska, were to join some more politically vulnerable Republican senators in voting against dismissing the articles of impeachment, they would undermine the Republican talking point that the impeachment lacks any valid factual or legal basis. Still, the public may not even see and hear the senators’ reasons for voting against dismissal. In the impeachment trial of former President Bill Clinton, for instance, the Senate chose — by a 53-47 vote — to bar the public from its debate. (So much for transparency.)

But if the Senate does not dismiss the charges, a ban on witnesses would be a stark break with precedent in every impeachment trial in American history, whether of presidents, judges or other officials; all have heard from witnesses. President Andrew Johnson’s impeachment trial in 1868, for example, heard from 25 witnesses for the prosecution and 16 defense witnesses. In the Clinton impeachment, the Senate allowed testimony from three named witnesses — accuser Monica Lewinsky and Clinton associates Vernon Jordan Jr. and Sidney Blumenthal— each of whom testified in nonpublic videotaped depositions, excerpts of which were presented in the public Senate trial.

In following the Clinton model — as McConnell initially promised — no bombshell moment would have occurred in the Trump trial even if Bolton or Mulvaney had testified, because their evidence would have been prepackaged in a deposition rather than heard live by the senators. Thus, even grudging Republican support for these limited witnesses under that model would win no accolades from swing voters, and would still alienate staunch Trump supporters who simply want a “win” for their side.

If the Senate ultimately voted to hear any witnesses, the Republican senators who supported that would likely be attacked by President Donald Trump’s ardent base for flip-flopping and abandoning him; a Senate trial with witnesses would infuriate the White House and defeat the pledge by Sen. Lindsey Graham, R-S.C., to make impeachment “die quickly” in the Senate. And the change might not garner its Republican advocates much support from independent or Democratic voters because their vote for witnesses will be belated and limited, undermining any benefits for the politically vulnerable.

All of this suggests that McConnell’s tactics may well ensure that Trump will not be convicted by the Senate, but at the cost of losing the Senate majority in the next election, despite his reputation as a master tactician. That reputation was undermined on day one of the Senate trial, when he failed to prevent House managers from using hours of prime-time television coverage Tuesday to lay out — in telling detail — the factual evidence underlying the impeachment article of abuse of power without using a single minute of the 24 hours they’re allowed under the Senate rules to formally make their case against the president. (That presentation began Wednesday.)

But more importantly, McConnell stumbled in failing to protect his Republican Senate colleagues and, in doing so, may have failed to protect his own seat of power.

It will be a heavy price for McConnell to pay if he is relegated to a minority leader role after November (assuming he wins his own re-election in Kentucky) in order to assure that Trump stays in office. It may be an even heavier price for all Republicans to pay if Trump is re-elected, and then faces both a Senate and a House controlled by Democrats.

Related:

• Democrats need to call Trump's bluff on impeachment witnesses

• The GOP's Senate impeachment trial strategy got blown up by Trump's legal team — for good reason

• Trump's impeachment is depressingly partisan. Here's why his removal doesn't have to be.