Elizabeth Warren is emerging as a major contender for the Democratic 2020 presidential nomination: A new poll shows the senator from Massachusetts nipping at the heels of the frontrunner, former Vice President Joe Biden, and other reports suggest she's attracting more media attention and enthusiastic crowds than most of her rivals in the race.

She's done this mostly — famously — by having "a plan for that." Among her many proposals, Warren has detailed plans to offer universal daycare for young children, free college for young adults, and affordable housing for everybody else. She even has a plan to pay for all those plans: a tax targeted at America's wealthiest families.

Even if you disagree with Warren's plans, there's something to admire about her approach. She's spelling out, to an unusual degree, how she would try to govern if she were to become president. Rather than choose between a campaign of substance or a campaign built on attitude, Warren is demonstrating that attitude can be demonstrated through substance.

"She's got chutzpah," said one of Warren's fans at one of her Iowa appearances over the weekend.

But the very thing that makes Warren's campaign stand out — all those big ideas — is also what makes her potential presidency vulnerable. It's easy to fall short of big goals, and politicians who make big promises and fail to keep them can easily be labeled "ineffective." No doubt if Warren takes the presidency, Senate Majority Leader Mitch McConnell (R-Ky.) will be waiting on Capitol Hill to ensure all her plans never become reality.

McConnell is really good at thwarting the Democratic agenda. Perhaps the biggest accomplishment of his career was blocking former President Obama's nomination of Merrick Garland to the Supreme Court — an act that ultimately let President Trump fill the opening left by the death of Justice Antonin Scalia, which in turn helped ensure the likely conservative control of the Supreme Court for the next generation. More recently, McConnell has been effective in stopping legislation originating in the Democratic-led House of Representatives. McConnell's not-so-secret technique: He simply doesn't let legislation he doesn't like come to a vote in the Senate.

Expect more of the same if Warren — or any other Democrat — wins the presidency next year.

"If I'm still the majority leader of the Senate, think of me as the 'Grim Reaper,'" he told Kentucky constituents in April. "None of that stuff is going to pass. None of it."

The more explicit Warren is about how she plans to govern, the more opportunity McConnell has to prepare to obstruct her efforts. So Warren, more than most candidates in the race, needs to have a plan ready to overcome such obstruction. To her credit, she has already come out for eliminating the filibuster in the Senate. Even if McConnell and Republicans lose control of that chamber next year, the continuing existence of the filibuster will allow them to block a good portion of the legislation Warren needs to accomplish her goals.

"When Democrats have the White House again, if Mitch McConnell tries to do what he did to President Obama, and puts small-minded partisanship ahead of solving the massive problems facing this country, then we should get rid of the filibuster," Warren said earlier this spring.

But that's just the beginning. If McConnell has a majority in the Senate, all bets are off.

So Warren — and other top Democrats — should be working harder now to woo the best candidates into 2020's Senate races, then campaign furiously to win Congress in 2020.

The problem, though, is that notable Democrats seem to be bypassing next year's Senate campaigns and aiming squarely for the White House. With the exception of Stacey Abrams, just about every Democrat you've ever heard of — and a few you haven't — are running for president. You can't win the races you don't run; Democrats seem to be conceding the Senate to the Republicans already. That's a shame, because the best way for a President Warren to have any real hope of enacting her agenda is to hope that Democrats win at the Congressional level in 2020. The only plan that really matters for a Democratic president, it turns out, is the plan that neutralizes Mitch McConnell.