It's moment-of-truth time.

Republicans always knew this election cycle would be tough for them, long before Donald Trump topped the GOP presidential ticket. And they enter the two-week home stretch trying to hang onto their slim majority while defending nine of the 10 races most likely to flip parties. And even as Trump confirms their worst nightmares by stoking controversy and sinking in the polls, Republicans have been hanging on in razor-thin races and gaining ground in states such as Arizona, Florida and Ohio. (Also true.)

But with two weeks to go, enough is starting to tip Democrats' way that it feels as though Republicans' uphill climb to hang onto their majority has suddenly gotten a lot steeper. A lot. Here are four advantages Democrats have right now, as they appear to be pulling away in the battle for the Senate:

1. The cash advantage

Hillary Clinton arrives at a fundraiser in August at the home of Justin Timberlake and Jessica Biel in Los Angeles. (Carolyn Kaster/Associated Press)

With two weeks to go, Trump is going to stop raising money for the Republican Party — in other words, stop raising money that can go to both his campaign and toward down-ballot races. Trump is not the world's most prolific fundraiser, but he is the Republican presidential nominee. So for him to stop fundraising right now means Republicans won't have a significant influx of cash at a significant time. And Senate Republicans were already in hope-and-pray mode when it comes to late-game TV money.

Other groups are stepping in to fill some of the void, but the price to play this late doesn't come cheap. Politico reported Tuesday that the Senate Leadership Fund, a GOP Senate super PAC with ties to Senate Majority Leader Mitch McConnell (R-Ky.), is dumping an eyebrow-raising $25 million into six races to try to buoy some of the most vulnerable candidates.

The money won't go as far now as it would have earlier this year; it's expensive to buy ads at the last minute, when supply is limited, and TV stations jack up their prices.

Steven Law, the head of SLF, acknowledged as much to Politico's Alex Isenstad, saying, "This isn’t a cheap date."

It's also an open question how much resonance this late-hour dump will have. Early voting is happening in 27 states, with more states opening their polls this week. Millions of ballots have been cast.

Meanwhile, some of the biggest players in GOP politics — the Koch brothers — aren't on the airwaves. They're spending their resources on the ground game for down-ballot candidates, not TV ads.

2. The Hillary Clinton advantage

Hillary Clinton campaigns in Florida on Oct. 25. (Melina Mara/The Washington Post)

While Trump's campaign is ramping down, Clinton's campaign is ramping up. Her last fundraiser was Tuesday night, but her campaign has scheduled 41 high-profile surrogate fundraisers between now and Nov. 3, report The Washington Post's Matea Gold, Sean Sullivan and Jonn Wagner.

And, increasingly confident that she will win on Nov. 8, Clinton is spending more time, money and resources on helping congressional candidates. In recent stops in Pennsylvania and New Hampshire, Clinton has saved a few moments to talk about the Senate races there. The Post's Paul Kane reported that Clinton's allied super PAC, Priorities USA, is dipping into some key House races.

As Clinton has shifted her focus, she also has shifted her message on Trump. And that's a critical puzzle piece for down-ballot Democrats.

Senate and House Republicans have done a decent job of separating themselves from Trump. If Trump loses by four to five points in states such as New Hampshire and Pennsylvania, there's evidence the that Republican candidates could hang on. Some Democrats thought Clinton was helping Republicans run from their nominee when she cast Trump as an anomaly of the Republican Party.

Now, she's pitching him as a creation of the Republican Party, a message that is obviously much more helpful to down-ballot Democrats' purposes. It's also one more example of how Democrats are getting in sync these final two weeks. That's a dangerous prospect for Republicans, who, to put it mildly, are not in sync.

3. The map advantage

Then there's the map itself. We've gone back and forth this fall about which party is favored to take the Senate, but one thing has remained constant: Democrats have more opportunities to win seats than Republicans do.

Here's the math: If Clinton wins, they need to net four seats to take back the majority. Democrats have a chance to win five to seven.

What's more, the well-respected, nonpartisan Cook Political Report announced Tuesday that it thinks Democrats don't just have a shot in those seats, they are actually poised to pick up those five to seven seats: "We feel that the prospect that Democrats will have at least 51 seats is greater than the odds of a tied Senate, or of Republicans somehow holding their majority."

4. The toss-up advantage

The Fix's latest Senate race ratings has six toss-up races. But "toss-up" can be a misleading term. Recent history suggests that one party tends to win a majority of Senate toss-up seats.

The Cook Political Report looked at the outcome of races from 1998 to 2014 and found that in every election, one party won at least two-thirds of their designated toss-up races. In six of those nine elections, the party won at 80 percent or more of the toss-up races.

In other words, toss-up races aren't a jump ball where statistically half the balls go to one team, half to the other. They're more accurately viewed as races that tend to go to the party that has the momentum in the election.

Right now, that's the Democrats. Which means that if Senate Republicans are panicking, they have good reason to be.