The longest government shutdown in U.S. history is a battle between two immovable objects: Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE and congressional Democrats. Trump understands his base will fracture if he relents on building a wall along the southern border. And Democrats understand they will fracture if they surrender to Trump in their first post-midterm test against a previously unchecked president.

The ace in Trump’s back pocket — declaring a national emergency — risks getting tied up in the courts, which helps explain why he hasn’t yet played this card: doing so would almost assuredly bring the shutdown to a swift halt. By delaying his declaration, Trump hopes the deepening pain of the shutdown will put greater pressure on, principally, House Speaker Nancy Pelosi Nancy PelosiMcConnell focuses on confirming judicial nominees with COVID-19 talks stalled Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Pelosi must go — the House is in dire need of new leadership MORE (D-Calif.) to make a deal.

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But congressional Democrats have their own ace, though playing it requires a heckuva lot more skill and patience. Still, this unplayed card could be our only way out of this mess.

Democrats’ last, best hope is to assemble a veto-proof congressional coalition to fund the rest of the government. That means two-thirds support in the House (290 votes) and two-thirds support in the Senate (67 votes). At first glance, this seems nearly impossible, as Democrats would need 55 GOP votes in the House and 20 GOP votes in the Senate. They would also need Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellMcConnell focuses on confirming judicial nominees with COVID-19 talks stalled McConnell accuses Democrats of sowing division by 'downplaying progress' on election security Warren, Schumer introduce plan for next president to cancel ,000 in student debt MORE (R-Ky.) to bring such legislation up for a vote — twice: once in the first phase and then again after Trump vetoes it.

However, a carefully orchestrated effort to mobilize politically frightened and vulnerable Republicans could prove successful, because currently the GOP is losing this fight. A Washington Post — ABC News poll released Sunday shows 53 percent of respondents blame Trump and congressional Republicans for the shutdown, while only 29 percent blame congressional Democrats. The longer this shutdown goes, the more damaging it will be to the country. While the 2020 election is nearly two years away, the shutdown is the type of earth-shattering national event that voters won’t forget in 20 months. And, regardless, Democrats won’t let them forget.

Which means even moderately vulnerable Republicans up for re-election will face a stark choice: Be part of the problem or part of the solution.

The Democrats’ solution would entail luring 55 House Republicans to finish funding the government. It would be a grand statement intended to shock vulnerable Senate Republicans into submission, thereby weakening McConnell’s seemingly unyielding grip on the legislative calendar.

Where will these 55 GOP votes come from? Well, in the 2018 midterms, 58 Republicans prevailed by 11 percent or less versus their Democratic rivals and just more than half of these 58 won by 5.5 percent or less. As soon as today, Democrats could begin pressuring these 58 members to abandon Trump before Trump abandons them — knowing that opposing government funding could be politically catastrophic for these mostly purple-district Republicans.

Securing 20 Republican Senate votes seems more far fetched. Who, besides perhaps Susan Collins Susan Margaret CollinsThe Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally Gideon leads Collins by 12 points in Maine Senate race: poll Senate leaders quash talk of rank-and-file COVID-19 deal MORE (R-Maine) and Lisa Murkowski Lisa Ann MurkowskiGOP ramps up attacks on Democrats over talk of nixing filibuster OVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' House Democrats tee up vote on climate-focused energy bill next week MORE (R-Alaska), could be expected to buck their president on what surely will be viewed as a litmus test for party loyalty?

But this party is facing extraordinary political headwinds on a number of fronts. For starters, they must defend 22 out of 34 Senate seats in 2020. The bigger story, however, is Trump’s growing unpopularity in many of these states. A recent t gives Trump net negative approval ratings in nine states he won in 2016: Florida (-3), Georgia (-3), North Carolina (-3), Ohio (-3), Pennsylvania (-6), Arizona (-7), Iowa (-10), Wisconsin (-12) and Michigan (-12). It’s an extraordinary reality for a president who desperately needs to win eight of these nine states next November.

It also spells trouble for swing-state Republicans whose electoral fortunes increasingly could hinge on an unpopular president. Three GOP-held seats at play in 2020 are among these nine. Another four are in states that barely support Trump (+2 to +4 net approval). And another three are in states Trump lost in 2016.

Looking ahead to 2022, 11 more GOP seats fall into one of these three groups: net-negative Trump approval, barely positive Trump approval, or states Trump lost in the last presidential election.

That makes 21 semi- to highly vulnerable Republican senators. Democrats need to pick off 20 to guarantee a veto-proof majority.

While unlikely given today’s political climate, this approach could yield success if the shutdown leads to more economically and politically catastrophic scenarios: the nation losing its triple-A bond rating, the stock market in free fall and the ripple effect of millions of Americans going unpaid for weeks or even months.

Do not underestimate the power of nationwide outrage born from financial desperation. And when that outrage is directed primarily at one party, political survival becomes the greatest motivator — in this case, a large minority of anxious Republicans abandoning the wall and thereby the president, to restore order to the republic.

B.J. Rudell is associate director of POLIS: Duke University’s Center for Political Leadership, Innovation and Service. His nearly 25-year career has included stints on Capitol Hill, on a presidential campaign, in a newsroom, in classrooms and for a consulting firm. He has authored three books and has shared political insights on CNN, Fox News and dozens of radio stations across the country.