Kamala Harris' economic agenda may now depend on beating Ted Cruz or Rick Scott

• Senate Democrats are about to spend millions in a bid to defeat Sens. Ted Cruz and Rick Scott.
• It may be their last, best hope at maintaining Democratic control of the upper chamber.
• Without that, a President Kamala Harris wouldn't be able to do much on the economy or abortion.

Vice President Kamala Harris has made a number of promises as part of her proposed domestic agenda.

Consider Harris' "opportunity economy" plan , which includes, among other things, a $6,000 child tax credit, a $50,000 tax deduction for small businesses, and a $25,000 tax credit for first-time home buyers.

She's also pledged to sign a bill to restore abortion rights and supports eliminating the Senate's 60-vote "filibuster" rule to do so.

But all of that depends not just on Harris defeating former President Donald Trump, but also on her party winning control of the House and Senate. And the battle for the upper chamber is looking especially tough for Democrats.

With Sen. Joe Manchin's retirement, Republicans are essentially guaranteed to win at least one seat. But Democrats would be able to maintain at least a 50-50 balance of power — with Gov. Tim Walz serving as a tie-breaking vote as vice president — if two of their incumbents were to hold on: Sen. Sherrod Brown in Ohio, and Sen. Jon Tester in Montana.

Brown has generally led his opponent in polling, but in recent weeks, Tester has fallen behind Republican candidate Tim Sheehy .

That's left Democrats with little choice than to go on offense and try to beat Sen. Ted Cruz in Texas and Sen. Rick Scott in Florida.

On Thursday, the Democratic Senatorial Campaign Committee (DSCC) announced a "multi-million dollar" investment in TV ads in those two states. Sen. Gary Peters of Michigan, the chairman of the DSCC, said his party was "expanding the map and going on offense."

"Democrats have strong candidates running effective campaigns in both states, and as we escalate our communications against Sens. Cruz and Scott we will crystallize the case against them," Peters said.

In Texas, Cruz faces Democratic Rep. Colin Allred, who was recently endorsed by former Republican Rep. Liz Cheney. In Florida, Scott's facing former Democratic Rep. Debbie Mucarsel-Powell.

Both races are seen as competitive but leaning toward Republicans. A source close to Scott signaled that the Florida senator isn't sweating it, telling Business Insider that "if national Democrats decide to spend in Florida, Rick Scott will spend more."

One of the richest members of Congress , Scott spent more than $60 million on his own race in 2018.

A Cruz campaign spokesperson hit Democrats for "coming in from their ivory towers in New York, DC, and California" to aid Allred.

It remains unclear exactly how much money Senate Democrats plan to spend in either state. Peters declined to get into specifics on Thursday, telling reporters that they're "not sharing that info right now for strategic purposes."

Harris, whose campaign has raised hundreds of millions of dollars since she entered the race, recently gave $10 million to the DSCC.