WASHINGTON — Well before President Donald Trump announced federal appeals court Judge Brett Kavanaugh as his second Supreme Court nominee, interest groups and activists on both sides were already rolling out plans to spend millions of dollars in key states on a campaign-like blitz to influence the outcome of the Senate confirmation fight to come.

With a razor-thin GOP majority, the fate of the nomination will largely be in the hands of two Republican senators and, just as critically, a handful of Democrats from states that voted for the president in the last election and who are facing the voters themselves this fall.

The Charles Koch-backed organization Americans for Prosperity announced Monday that it will spend "seven figures" on grassroots organizing, paid media and door-to-to door canvassing in the ten states that Democrats are trying to defend in November. And other political interest groups are planning a barrage of campaign ads as well as on-the-ground grassroots activities.

Among those Democrats bearing the brunt will be Sens. Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota and Joe Manchin of West Virginia.

All three face difficult races for re-election in November — and they were the only Democrats to vote for Trump’s first Supreme Court nominee, Neil Gorsuch, upping the pressure on them even higher.

Another senator already facing the onslaught is Doug Jones of Alabama, a rare Southern Democrat who won an improbable special election late last year against scandal-laden Republican Roy Moore.

Before Monday's announcement, those four were already the targets of at least $1.4 million worth of advertising from the conservative Judicial Crisis Network, an umbrella organization pushing for the confirmation of Trump’s nominee. The ad says, “extremists will lie and attack the nominee. But don’t be fooled.”

Trump’s nominee is “the best of the best,” the narrator continues In the ad that started airing before the announcement. And starting next Monday, another $1 million ad will run in those same states introducing Kavanaugh.

Carrie Severino, chief counsel for the network, told NBC News the organization spent $10 million in advertising in support of Gorsuch and they are prepared to spend “whatever it takes” to ensure that Kavanaugh is confirmed.

“Are they going to align themselves with the far left wing of their party?” Severino asked of the Democrats. “We don’t think that’s going to be popular in their states.”

Donnelly, Heitkamp and Manchin were invited to the White House Monday night for the roll out of the nominee, but all three declined the invitation. Heitkamp and Manchin said they didn’t want their first meeting with the nominee under those circumstances.

“I just got back (to Washington) and I’ve got a bunch of stuff I need to do and it’s not a place where I think you can do any due diligence,” Heitkamp said.

Jones said it’s “sad” that so much money will be spent in his state and others.

“That money could be spent in so many other positive ways other than media advertising to try and sway somebody,” Jones said. “I’m going to exercise my role. I’m going to do my due diligence and I’m going to exercise my judgment independently and do the thing that I think is the right thing and then once I make my decision that’s when I’ll explain it to voters.”

Progressive groups are planning their own effort to defend the Democrats from attacks — and to urge them to vote against Kavanaugh.

Demand Justice, run by former Senate Minority Leader Chuck Schumer aide Brian Fallon, is working with NARAL Pro-Choice, MoveOn, Indivisible, and other progressive groups. They have pledged at least $5 million to be used, in part, in North Dakota, Indiana and West Virginia.

Marge Baker, executive vice president of People for the American Way, a group helping to organize grassroots protests in states around the country, said, “There’s enormous energy in the progressive community on this — far more than Gorsuch.”

Democrats argue that Trump’s nominee will tilt the court to the right because retiring Justice Anthony Kennedy was considered a swing vote. While he did side with the conservatives in many decisions, he was the deciding justice in many landmark cases, including one that upheld Roe v. Wade as well as a marriage equality case.

Other Democrats with competitive races are also expected to face attacks. Trump's campaign arm, America First, confirmed a seven-figure ad buy that will additionally target Sen. Jon Tester, D-Mont., and Claire McCaskill, R-Mo. in coming weeks.

McCaskill and Sen. Bill Nelson, D-Fla., were painted quickly by their GOP opponents as hypocritical partisans — willing to confirm President Barack Obama’s judicial nominees, only to stonewall Trump.

A new TV and digital ad from the campaign of Gov. Rick Scott, who is challenging Nelson, accuses Nelson of “toeing the line” for Democrats, while Missouri GOP Attorney General Josh Hawley launched a website called “Supreme Claire” to highlight McCaskill's history of judicial conformation votes.

Hawley’s campaign went further on Monday, putting up his first TV ad of the cycle and taking on McCaskill directly for endorsing “activist liberals every time.” A Hawley spokesperson told NBC Monday they’re comfortable talking about the courts heading into November, given Hawley's current position and his time as a Supreme Court clerk for Chief Justice John Roberts.

And the Senate Majority Fund, backed by Senate Majority Leader Mitch McConnell, has indicated that it also plans to engage in the SCOTUS fight.

For their part, progressives are also going on the offensive against the two critical Senate Republican votes — Sens. Susan Collins of Maine and Lisa Murkowski of Alaska. Both have said that upholding the precedent of the Roe v. Wade decision is an important factor in their vote, putting them in the cross hairs of Democrats who think they could win them over if the law is under threat.

So far, the senators have largely shrugged off the incoming onslaught. Manchin said it’s not going to influence his decision on how he’ll vote on the nominee.

“I’m bound basically to whatever I can go home and explain,” Manchin said. And while he will likely spend the next several weeks under intense scrutiny over the nomination, he says he won’t announce his decision until he casts his vote.