Five Northeastern and mid-Atlantic states, dubbed the Acela Corridor block after the Amtrak line that serves them, will go to the polls Tuesday. If polls are any indication, the results will cement the delegate leads of Democrat Hillary Clinton and Republican Donald Trump.

Both Trump and Clinton hold wide leads in surveys of voters in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island—the states voting on Tuesday and five of the remaining 14 (or 15 on the Dem side if you count D.C.) contests left in the primaries.

The anticipated victories come on the heels of blow out wins for both frontrunners in their shared home state of New York April 19 and will increasingly narrow the already implausible paths of their challengers, Vermont Sen. Bernie Sanders on the left and Texas Sen. Ted Cruz and Ohio Gov. John Kasich on the right.

Given the predictability of the contests at the top of the ticket, much of the drama on Tuesday will be playing out in down-ballot races, particularly in a pair of hotly contested Senate Democratic primaries in Maryland and Pennsylvania.

In Maryland, U.S. Reps. Donna Edwards and Chris Van Hollen are vying to fill retiring Barbara Mikulski’s seat. Mikulski, the longest serving woman in Congress and the dean of the Senate women, has long voiced hopes that a woman would succeed her. Though she has not endorsed in the primary, she lambasted Senate Minority Leader Harry Reid last year for endorsing Van Hollen.

Many women’s groups aim to retain seats held by women for women. The super PAC attached to Emily’s List, which helps elect pro-choice female candidates, has spent $3 million for Edwards. Polls show Van Hollen and Edwards in a photo-finish race, and with little serious GOP opposition in the general election, meaning whomever prevails in the Democratic primary is the likely next senator.

In Pennsylvania, another Democratic senatorial primary looks to be a nail biter. With the backing of the entire establishment including President Obama, former Pennsylvania environment secretary Katie McGinty took a narrow lead this week over former Congressman and retired Navy admiral Joe Sestak. The winner of that race will challenge incumbent Republican Sen. Pat Toomey, who beat Sestak for that seat in 2010 by just two percentage points.

McGinty and Edwards are two of eight women Emily’s List and other women’s groups are hoping to elect to the Senate this cycle on Clinton’s coattails, potentially expanding the number of women in the Senate to 26 from 20 this year.

Establishment Republicans, many of whom are already writing off the presidential race whether Trump or Cruz is at the top of the ticket, are throwing much of their resources into protecting the Senate, which they control by four seats. The map is not an easy one for them: the GOP must defend seven seats in states won by Obama in either 2008 or 2012. Political forecasters already rank as “leaning Democratic” two races: WisconsinSen. Ron Johnson, who is facing former Sen. Russ Feingold, and Illinois’ Sen. Mark Kirk, who is being challenged by Rep. Tammy Duckworth. Another five races are rated toss-ups.

Democrats have also been doing some last-minute candidate recruitment for the House, seeking stronger challengers particularly in potentially vulnerable districts such as Pennsylvania’s eighth and 16th districts, which are open seats, and against freshman Ryan Costello and sophomore Pat Meehan, who represent exurban Philadelphia suburbs in Pennsylvania’s sixth and seventh districts.

(Van Hollen’s old House seat isn’t a toss up—it will likely go Democratic—but it is home to the most expensive House race thus far of the cycle. The contest to represent the largely wealthy district, which abuts Washington, D.C., has several prominent names, including Kathleen Matthews, wife of NBC host Chris Matthews and a former local television personalty herself; a self-funding wine millionaire who has throw $12 million into the race; a former Obama Administration official; and a state senator.)

But Republicans note with a sigh of relief that Democrats have realized far too late that this is potentially a wave year. Thus far only 21 GOP seats are rated lean Democratic or toss up, with Democrats needing at least 30 to regain control of the House. If they’d done more candidate recruitment earlier, they could have been in a better position to take the House. To boot: in February of this year Dems were glumly ceding control of the House, versus Republicans who were already looking for the 2010 wave by that spring that allowed them reclaim the House that year.

Then again, few Republicans—let alone Democrats—would’ve predicted a year ago that Trump would be poised at this point in April to sweep the Acela primaries and would be the most likely GOP presidential nominee.

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