Convict Trump—or else.

That’s the message liberal advocacy groups are trying to send to Republican senators in hopes of pressuring them to vote for President Trump’s removal from office, or at least maximizing the political pain for them if they don’t.

One such group, Stand Up America, is bankrolling a new $300,000 digital campaign targeting a dozen GOP senators as the impeachment trial draws nearer. The liberal political nonprofit, which has been organizing to support impeachment and other initiatives to counter Trump, tells The Daily Beast it plans to run digital ads urging the public to call their senator; they will also launch a volunteer-driven texting campaign to drive calls and apply pressure on a few key Republicans.

It’s part of a broader effort from the left to lean on Republican senators to break with Trump in a trial that will decide the fate of his presidency. Chances are, it won’t work; so far, no Republican lawmaker has publicly indicated a willingness to vote for Trump’s conviction after the House voted to impeach earlier this month. And groups aligned with the president have begun to crowd the airwaves with anti-impeachment messages targeting moderate Democrats.

“Hope springs eternal,” said Jim Manley, a Democratic strategist and alumni of former Sen. Harry Reid’s office. “But if I look at what happened in the House, I’m afraid we’re in for a beating.”

But liberal groups, some of which have deep pockets and deeper volunteer networks to tap into, could at the very least make the next few weeks even more difficult for a few Republicans. Stand Up America is putting a special focus on GOP senators facing competitive re-election races in 2020—such as Sen. Joni Ernst of Iowa and Sen. Cory Gardner of Colorado—or those who have indicated possible support for impeachment, like Sen. Mitt Romney of Utah and Sen. Lisa Murkowski of Alaska.

The broader pool of senators targeted by Stand Up America includes Sen. Susan Collins of Maine, who is both up for re-election in 2020 and is considered a possible vote to convict Trump, and Sen. Lamar Alexander of Tennessee, a moderate who is retiring at the end of next year.

The announcement of this opening salvo comes as Democrats emerge from a House impeachment vote largely unified but politically battered after GOP groups dumped millions of dollars on ad campaigns targeting vulnerable Democrats for their support of impeaching Trump.

There was some grumbling that liberal outside groups did not provide enough air cover for the dozens of Democratic lawmakers representing Trump-won districts for whom impeachment was a politically difficult vote. But the dynamics are far different in the GOP-controlled Senate, where Democrats see an opportunity to finally go on the offensive.

A second advocacy group, backed by the billionaire presidential candidate Tom Steyer, has indicated it will spend whatever it takes to mount a successful pressure campaign on GOP senators. Steyer’s group, Need to Impeach, laid down $350,000 for a cable TV ad campaign last week and has committed to spending $1 million heading into the trial. Steyer has already spent $3.5 million targeting GOP senators.

“We’ve got a few million to put pressure on senators to do the right thing,” said Kevin Mack, the lead political strategist at Need to Impeach.

They plan to apply that pressure not just around the final vote to acquit or convict Trump, but on procedural votes that will define what the trial itself looks like. Since the House approved articles of impeachment last week, Speaker Nancy Pelosi has held off on formally sending them to the upper chamber while the GOP majority leader, Sen. Mitch McConnell of Kentucky, and his Democratic counterpart, Sen. Chuck Schumer of New York, try to negotiate ground rules for the trial.

Their disagreement centers on whether or not new witnesses in the Ukraine inquiry will be called to testify. Schumer has said he will use his limited power as minority leader to force votes in the Senate on subpoenaing key figures like acting White House Chief of Staff Mick Mulvaney, who has so far refused to testify.

“The American public has made it clear they want to see witnesses and get to the bottom of what happened,” said Mack. “We will put pressure on individual senators who have a vote to take.”

Democratic veterans of Senate politics are hopeful this is a sign that their side’s constellation of advocacy groups will not get put on the back foot by a deluge of GOP cash. During the House fight, liberal groups seemed outgunned at key stretches, said Manley.

Outside groups, he said, should “focus on either persuading or providing as much political pain as possible to a handful of Republicans who are out there, who may or may not be persuadable.”

Over the course of the House inquiry, political groups connected to Trump and the GOP dumped close to $17 million on ads attacking vulnerable House Democrats on impeachment, according to The New York Times . Democrats hardly spent anything to pressure House GOP lawmakers, and instead ran ads touting the party’s record on issues like health care.

Ultimately, just two House Democrats voted against both articles of impeachment, and one of them, Rep. Jeff Van Drew of New Jersey, immediately switched to the GOP afterward.

Political action committees associated with the GOP and Trump’s re-election campaign will continue to be involved during the Senate trial. In an unexpected development, former New Jersey Gov. Chris Christie is entering the fray to launch a new pro-Trump big money group aimed at providing air cover for GOP senators and hitting a group of moderate Democratic senators.

Last week, Christie’s group placed a million-dollar TV ad buy to back up senators like Collins and Gardner but also to pressure Sen. Doug Jones, a Democrat facing a tough re-election battle in deep-red Alabama.

Those on the pro-impeachment side say they’re not fazed by that effort. “Our message is, bring it on, let’s go,” said Mack. “If Chris Christie wants to start running ads covering up Donald Trump’s crimes, it’s not going to go well in Colorado and Maine.”

Impeachment advocates also say they have an advantage that newly-formed PACs like Christie’s do not: an established presence in the world of anti-Trump grassroots politics, which can be called upon for fundraising, organizing, and more.

Stand Up America claims to have a network of 2.5 million people it will mobilize to pressure GOP senators around the impeachment trial. The group notes that it has driven more than 200,000 constituent calls demanding impeachment to Capitol Hill already.