Vulnerable red-state Democrats are facing a mountain of pressure as confirmation hearings for Judge Neil Gorsuch, President Trump's Supreme Court nominee, start on Monday.

Both sides are homing in on a group of roughly 10 Democrats who are up for reelection in 2018 in states carried by Trump and who could make or break his nomination.

Democratic leadership signaled within hours of Trump naming Gorusch to fill the seat left vacant by Justice Antonin Scalia that they would fight his nomination and require him to get 60 votes to clear the upper chamber. That means Republicans will need to break off at least eight Democrats.

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The pressure from outside groups is putting the Democrats up for reelection between a rock and a hard place: Any move to support Gorsuch will inflame the party's progressive base, but opposing him will be fodder for Republicans and outside group ahead of 2018.

Democrats have been meeting with Gorsuch but are staying on the fence about whether they will support him.

Democratic Sens. Bob Casey Robert (Bob) Patrick CaseySecond GOP senator to quarantine after exposure to coronavirus GAO report finds brokers offered false info on coverage for pre-existing conditions Catholic group launches .7M campaign against Biden targeting swing-state voters MORE (Pa.) and Joe Manchin Joseph (Joe) ManchinBiden promises Democratic senators help in battleground states Senate leaders quash talk of rank-and-file COVID-19 deal OVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' MORE (W.Va.) — who are both up for reelection in 2018 — were confronted by liberal constituents during in-state town halls over the past week but insisted they wouldn’t make a decision until Gorsuch testifies.

Senate Minority Leader Charles Schumer Chuck SchumerMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security Warren, Schumer introduce plan for next president to cancel ,000 in student debt Schumer lashes out at Trump over 'blue states' remark: 'What a disgrace' MORE (D-N.Y.) predicted that most of his 48-member conference will stay undecided through next week, telling Fox News’s Bret Baier, “I think people are waiting for the hearing.”

But outside groups are already flooding the zone, using a mix of phone calls, mail, web and TV ads, as well as editorials with in-state newspapers, to try to sway key senators.

With Republican leadership wanting to confirm Gorsuch before senators leave for two weeks on April 7, tensions could boil over as Trump’s nominee heads for a final showdown on the Senate floor.

A resurgent liberal wing of the party is sending early warning shots over Gorusch, saying that they view any vote for him as a vote against party values — and for Trump.

“We’re counting on Democrats to hold a really, really strong line. ... We’re going to be watching really closely,” said Heidi Hess, Credo Action’s senior campaign manager.

She added that the group would be relaunching calls targeting a key group of senators on Monday, the first day of Gorsuch’s hearing.

In addition to red and purple state Democrats, Hess said they were also pushing Sen. Dianne Feinstein Dianne Emiel FeinsteinSenators offer disaster tax relief bill Democrats back away from quick reversal of Trump tax cuts Congress must save the Postal Service from collapse — our economy depends on it MORE (D-Calif.) — the top Democrat on the Senate Judiciary Committee — to help “set the tone.”

“The progressive base is counting on you, and we will have your backs” if vulnerable Democrats vote against Trump’s nominee, Hess said. But she also warned senators that activists will “hold them accountable” if they vote for Gorsuch.

“I think we see this as enabling Trump to help achieve his agenda,” she said. “The court is the longest lasting way that Trump could institutionalize his hateful agenda.”

Credo Action has paired up with more than a dozen other Democratic outside groups to launch the “People’s Defense” urging Democratic lawmakers to take a tougher stand against Gorsuch.

The Progressive Change Campaign Committee (PCCC) has done polling in 2018 states arguing that most voters would oppose Gorsuch if he’s painted as pro-corporation and anti-worker.

“The basic message was that red-state Senate Democrats will be standing on very strong ground if they vote against Gorsuch and do so on economic populist grounds,” said Adam Green, the co-founder of the PCCC.

Green added that the PCCC has focused its lobbying on Senate leadership and red-state Democrats, stressing that if vulnerable lawmakers come out early against Gorsuch it could help set the tone for the rest of the 48-member conference.

“If a majority of the red-state Democratic senators do the right thing that gives mental license to their entire rest of the Democratic caucus to follow their lead,” he said.

He warned that if "if people like Heidi Heitkamp Mary (Heidi) Kathryn HeitkampCentrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents Susan Collins set to play pivotal role in impeachment drama MORE and Joe Manchin vote with Trump for Gorsuch, that hurts the reelections of Tammy Baldwin Tammy Suzanne BaldwinKeep teachers in the classroom Cher raised million for Biden campaign at LGBTQ-themed fundraiser Democrats seek balance in backing protests, condemning violence MORE, Sherrod Brown Sherrod Campbell BrownEmboldened Democrats haggle over 2021 agenda Hillicon Valley: Russia 'amplifying' concerns around mail-in voting to undermine election | Facebook and Twitter take steps to limit Trump remarks on voting | Facebook to block political ads ahead of election Top Democrats press Trump to sanction Russian individuals over 2020 election interference efforts MORE, Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE and others up for reelection in 2018."

But Democrats and aligned outside groups are being badly outspent on TV advertising ahead of the hearings. GOP and conservative groups have spent more than $3.3 million, according to CNN, compared to $180,000 from Democrats.

And conservative groups have launched rounds of TV and web ads targeting vulnerable Democrats in their home states.

The Judicial Crisis Network has pledged a total of $10 million to support Gorsuch’s nomination and to target Democratic senators. It’s already spent $4.4 million on ads for Gorsuch, including a $2 million ad buy targeting vulnerable Democratic Sens. Claire McCaskill Claire Conner McCaskillDemocratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally Missouri county issues travel advisory for Lake of the Ozarks after Memorial Day parties MORE (Mo.), Joe Donnelly Joseph (Joe) Simon DonnellyEx-Sen. Joe Donnelly endorses Biden Lobbying world 70 former senators propose bipartisan caucus for incumbents MORE (Ind.), Heidi Heitkamp (N.D.) and Jon Tester Jonathan (Jon) TesterPence seeks to boost Daines in critical Montana Senate race This World Suicide Prevention Day, let's recommit to protecting the lives of our veterans Filibuster fight looms if Democrats retake Senate MORE (Mont.).

The National Republican Senatorial Committee is using the issue as ammunition against red-state Democrats they hope to unseat, including funding radio ads and billboards against McCaskill, Donnelly, Casey and Sen. Debbie Stabenow Deborah (Debbie) Ann StabenowGAO report finds brokers offered false info on coverage for pre-existing conditions Democrats back away from quick reversal of Trump tax cuts Battle looms over Biden health care plan if Democrats win big MORE (D-Mich.).

Republicans aren’t expected to ease their political fire heading into the hearing. Two GOP-aligned groups — the National Rifle Association Freedom Action Foundation and the Great American Alliance — both announced late seven-figure ad buys.

Concerned Veterans for America, a group aligned with GOP mega-donors David and Charles Koch, is targeting Heitkamp, Manchin, McCaskill, Donnelly and Tester, as well as Sen. Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (D-Colo.) with web ads.

Though Bennet won reelection in 2016, Republicans are targeting him because of Gorsuch’s ties to the state and Colorado’s purple political leanings.

The conservative group America Rising Squared blasted out a video this week of Bennet leaving a town hall in Colorado, saying the Democrat “runs away” when a reporter asked about Gorsuch.

Bennet is expected to introduce Gorsuch at his hearing, as home state senators traditionally do. A spokeswoman said Friday that he remains undecided on the nomination.

A February poll showed a plurality of Americans say Gorsuch should be confirmed.

Republicans argue that Democrats can either support their constituents and vote for Gorsuch or fold to pressure from progressives and prove they’re too liberal for their states.

“With the hearings starting next week, Senate Democrats should end their political games and support an up-or-down vote in the full Senate,” said Rick Gorka, a spokesman for the Republican National Committee, in a note to reporters.

Liberal groups are also expanding their reach to target Republicans up in 2018.

The liberal Constitutional Responsibility Project launched a TV ad in Arizona, Nevada and Washington, D.C., urging voters to tell GOP Sens. Jeff Flake Jeffrey (Jeff) Lane FlakeRepublican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style Bush endorsing Biden? Don't hold your breath MORE (Ariz.) and Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (Nev.) to oppose Gorsuch if he won’t answer questions about his position on birth control.

And if the airwave war wasn't enough, red-state Democrats are facing direct pressure from their colleagues.

Sen. Elizabeth Warren Elizabeth WarrenWarren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon No new taxes for the ultra rich — fix bad tax policy instead MORE (D-Mass.) rallied outside of the Supreme Court with a coalition of liberal outside groups urging opposition to Gorsuch. And Schumer held an event with individuals he argued had been negatively affected by Trump’s nominee.

Progressive groups say they expect Democrats to stay united.

“The Supreme Court battle will be the biggest moment of truth so far for whether the Senate Democratic caucus as a whole will fight with backbone or be perceived as caving to Trump,” Green said.

“They’re all sinking or falling together.”