By Julian Zelizer, CNN Political Analyst

(CNN) -- President Donald Trump is requesting that Congress provide a whopping $18 billion to build a border wall as part of a $33 billion plan for border security. Democrats will need to decide whether obtaining security for immigrants who came as children -- known as Dreamers -- through a deal to preserve DACA is worth the high cost. President Trump, confident that he can make some sort of deal on immigration, said that he hopes "we can work out" an "arrangement with Democrats."

Yet Democrats should take stock and think about the implications of Michael Wolff's new blockbuster book, which makes a case that the President is unfit to hold office. They should consider the way Republicans pushed through an unpopular massive corporate tax cut in the final days of 2017. Both elements should throw some cold water on every congressional Democrat who is thinking about striking any kind of deal with the President.

Democrats need to agree on a strategy for how they will deal with a very conservative and very unstable President. With the midterm elections looming over everything that takes place between now and November, Democrats will have two basic choices on the table: make a deal or do their best to obstruct.

The obstruction route would take a page right out of the Tea Party playbook that worked pretty well for the GOP under President Barack Obama. This route, favored by progressive groups like Indivisible in battles such as health care, would have Democrats refuse to enter into any major negotiations over policy. President Trump's agenda would languish and deny him any legislative victories that Republicans can then run on in November.

The justification for this approach is that Trump represents policies and ideals that fundamentally contradict the values of the Democratic Party. Doing everything possible to limit the long-term success of this presidential term is more important than any benefits that might come from a short-term deal, especially one with provisions (such as money for a border wall) that don't sit well with much of the party. Given that turnout will be the key to the midterm elections, energizing the base can have significant political value.

Added to this rationale would be the argument that this White House cannot be trusted. Any offer that the President makes for a deal must be viewed with suspicion. He has not proven that he is a reasonable negotiator. Many Democrats will also remember the Obama years when the President, a believer in bipartisanship, kept offering olive branches to the GOP only to see them try to bite off his hand.

But the other choice -- making a deal -- is more appealing instinctively to many congressional Democrats who have devoted their lives to the Hill. With the President struggling to improve his approval ratings and Republicans desperate to avoid a wave election, their view is that Democrats should capitalize on the moment and take what they can get. Restoring DACA through legislation, even if that means allowing funding for a massive border wall, and maybe obtaining support for a decent infrastructure plan, are worth it, even if President Trump and the congressional Republicans can take these accomplishments to the campaign trail.

Most Democrats naturally lean toward compromise. This is the nature of a party that believes that government can solve problems. There is more at stake for Democrats than for many Republicans if policy stands still. As numerous social scientists have written, obstruction and stalemate meshes with the conservative agenda.

But the stakes feel enormous right now for many Democrats, and it's possible to imagine they will become the party of "no," despite the costs.

Many Democrats feel that this is the most dangerous Republican presidency in years, because Trump is successfully enacting a deregulatory and supply-side agenda that is cutting down regulatory policies favored by Democrats and because, as Wolff's book seems to confirm, the President is not someone who is fit to serve as commander in chief.

This is the moment to let Republicans handle their own problems and force the GOP, which does command a majority, to find their own ways to move forward with legislation. Democrats face a difficult choice of weighing the need to protect the Dreamers, whose futures now hang in the balance, with those who would be deported or never be able to arrive to the United States as a result of the deal.

Taking the obstruction path is extremely difficult. It will allow Republicans to try to tarnish the image of the Democrats as incapable of wielding power. President Trump will be thrilled to be able to blame Democrats for problems. His tweets have indicated he is raring to go. A few days ago, the President tweeted: "Democrats are doing nothing for DACA -- just interested in politics. DACA activists and Hispanics will go hard against Dems, will start 'falling in love' with Republicans and their President! We are about RESULTS."

But sometimes standing firm against a presidential agenda can have its virtues. Doing so, particularly with the slim majority that Republicans now have in the Senate, can be the most effective way to prevent a president from doing serious damage.

Given Trump's terrible approval ratings outside of the Republican base, denying him and the GOP any victories beyond the tax law could, more than anything, make sure Democrats retake control of Congress in 2018 and 2020.

If they make any deals that strengthen the President's agenda, the Republicans might retain control of Congress and help Trump push through legislation -- more draconian than the tax cut, the border wall, the refugee ban (an executive order) or anything else that has been proposed thus far -- in 2019. The dismantling of landmark programs like Medicare could be next. House Speaker Paul Ryan has already signaled that this is a priority in the coming years.

Playing legislative hardball with a president who has given legitimacy to extremist organizations and rhetoric, while circulating falsehoods about key issues like climate change and voting rights, is in itself an affirmative move in defense of the Democrats' core ideas. Refusing to negotiate with a president who is so willing to flex presidential authority beyond conventional boundaries is a means of trying to check the abuse of power.

Democrats are at a crossroads as the new year begins. Everything about the Trump presidency will hinge on the outcome of the midterm elections. If the strategy Democrats employ gives them control of the House and Senate, they will be able to fundamentally redirect national politics in the final two years of Trump's term. If they don't, and Republicans learn that despite all the chaos and radical decisions of this presidency, they can still do well with their electorate, all bets are off about how the next few years will unfold.

The-CNN-Wire

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