By Ted Barrett and Deirdre Walsh CNN

(CNN) -- Senate Democrats are vowing to stall action on eight of Donald Trump's Cabinet nominees tasked with carrying out his economic, law enforcement and regulatory agenda, a senior Democratic aide told CNN Monday.

If carried through, the threat that could delay confirming the President-elect's choices for months.

Those targeted include secretary of state nominee Rex Tillerson, attorney general pick Jeff Sessions and health and human services secretary hopeful Tom Price.

Democrats warn if they don't get the nominees' required background information and financial records and have adequate time to review them before confirmation hearings are held, they'll drag out confirmation votes with a series of procedural maneuvers.

While Democrats are unlikely to have the votes to block most of these nominees, their threat to delay the confirmation process of Trump's Cabinet could hamper the new administration, which has promised a fast start in undoing policies of outgoing President Barack Obama.

Senate Majority Leader Mitch McConnell plans confirmation votes on multiple nominees on the afternoon of Inauguration Day, something that could now be in jeopardy if Democrats carry out their threat of imposing procedural hurdles.

However, Republicans said they weren't convinced the delaying tactics from incoming Senate Minority Leader Chuck Schumer would succeed.

Any "attempt by Republicans to have a series of rushed, truncated hearings before Inauguration Day and before the Congress and public have adequate information on all of them is something Democrats will vehemently resist," Schumer said in a written statement. "If Republicans think they can quickly jam through a whole slate of nominees without a fair hearing process, they're sorely mistaken."

Tillerson, the ExxonMobil chief executive who has been criticized by Republicans and Democrats for his ties to Russian President Vladimir Putin, has drawn additional scrutiny from Democrats on the Senate Foreign Relations Committee for not turning in his tax returns for the past three years, something Republicans argue is not required of him. Sessions has also been blasted by Democrats on the Judiciary Committee for turning in what they say is incomplete background information from the Alabama senator.

The other six nominees targeted by Democrats: Rep. Mick Mulvaney, R-South Carolina, a spending hawk selected to be director of the Office of Management and Budget; Betty DeVos, an advocate of charter schools who is chosen to be secretary of education; Price, R-Georgia, the anti-Affordable Care Act champion chosen to be secretary of health and human services; Andrew Puzder, the fast food CEO chosen to head the Department of Labor; Steve Mnuchin, the former Goldman Sachs executive picked to head the Treasury Department, and Scott Pruitt, the Oklahoma attorney general who opposes many existing environmental regulations, who is the choice to head the Environmental Protection Agency. The list of nominees targeted by Democrats was first reported by the Washington Post.

Confirmation hearings for Sessions, Tillerson, DeVos and Pudzer are tentatively scheduled to begin next week.

How Democrats can slow the process

Once the committees have voted to send the nominations to the floor, Democrats, who have 48 seats compared to 52 for Republicans, can force delays for up to about one week per nominee, meaning it could take months to get through all the major posts.

But without GOP support, Democrats will be unable to use the ultimate stopping power of the filibuster to block nominees they oppose because in the last Congress they changed Senate rules -- over the objection of Republicans -- to lower the threshold of votes to overcome a filibuster of executive branch nominees from 60 to 51.

That means they best they can do is use procedural delays to stall a final confirmation vote.

They can insist on cloture votes for each nominee, and then use the entire amount of debate time allowed under the rules to delay speedy votes, and clog up floor time with lengthy floor speeches. This would mean each nominee could take up to a week to ultimately be confirmed and force McConnell to set aside other top legislative priorities -- like starting the process of repealing Obamacare.

Republicans also think the handful of Democrats from red-leaning states who are up for re-election in 2018 won't be willing to obstruct Trump's nominees.

"When President Obama was elected, Republicans and Democrats worked together and expeditiously to carefully consider his nominees. The Senate held hearings on multiple nominees before he was even sworn in. The Senate confirmed seven of his nominees on day one---and nearly all were confirmed within two weeks," said Don Stewart, a spokesman for McConnell. "Sen. Schumer and others approved wholeheartedly of this approach at the time, so surely they won't object to treating the incoming president's nominees with the same courtesy and seriousness with which the Senate acted on President Obama's nominees."

Democrats say that Obama's nominees were vetted earlier by the FBI and the Office of Government Ethics, which reviews potential financial conflicts by nominees, and that those results were turned over to the committee before the confirmation hearings were scheduled. Republicans note, however, that none of the confirmation hearings has been officially scheduled and that only tentative dates have been announced.

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