This presents a crucial test to the tea party movement that has reshaped American politics since 2008. The most obvious challenge is that Trump has chosen to leave Social Security and Medicare alone, two of the biggest components of the federal budget and two prime targets for conservatives like Speaker Paul Ryan.
Trump is going to assure Congress that the draconian cuts to domestic programs like the Environmental Protection Agency, reductions which tea party Republicans love, will balance out the huge increase in military spending. But the reality will be different.
President Ronald Reagan learned in the early 1980s that cutting government programs is extremely hard in practice. When Reagan slashed income taxes and boosted military spending, promising to balance the budget with domestic cuts, he failed. Reagan also backed away from cuts to Social Security and Medicare when he faced a political backlash for trying.
In the end, deficits skyrocketed in the 1980s. Reagan faced a Democratic House. Yet we have seen that Trump is already learning how hard it is to cut government, even in a moment of united partisan control, as he backs away from eliminating increasingly popular parts of the Affordable Care Act. In his speech to Congress, he also promised to move forward with a $1 trillion infrastructure bill, which surely won't sit well with fiscal conservatives in his party.
Finally, this increase in military spending is a significant expansion of the federal government. While tea party Republicans might want to distinguish national security from the rest of government, in reality if they swallow this proposal they are revealing that conservatism really is about what kind of government to support, not whether big government is bad.
Tea party Republicans insisted that they would be different and for much of the time that they have had representation in Congress since 2008 they have been true to the word. They have been an intensely ideological coalition, insisting on a commitment to purity on policy that left the Obama administration deeply frustrated and tied up in knots.
Added to all this is the curveball that the president threw when he announced that he is open to immigration reform that would allow a large number of undocumented immigrants to remain in the country. Despite his continued attacks on undocumented immigrants in his address, the mere mention of a proposal to liberalize policy is anathema to many Tea Party Republicans who represent constituencies that are sympathetic to hardline anti-immigration sentiment.
The Republicans went to great lengths to fight Obama on spending cuts. When Obama sought compromise, they stood their ground in the budget battles of 2011, threatening to send the federal government into default. Hawkish Republicans were equally frustrated with their tea party colleagues when Congress could not reach agreement on spending in 2013 and as a result of the rules put into place in 2011, forced the implementation of budget sequestration that imposed caps on military and not domestic spending.
When Republican leaders like former Speaker John Boehner showed that they were willing to give even an inch to the Democrats, the tea party toppled them from power.
The current Speaker, Paul Ryan, has built much of his career around promising tea party Republicans that he would move forward with "entitlement reform" (meaning Social Security, Medicare and Medicaid cuts) despite the political risks. He has been a zealot on this issue and hoped that this moment of unified government would offer an unprecedented opportunity. A frustrated Speaker Ryan, who said after the election that Trump had a "mandate," has now warned: "I've been a big time entitlement reformer for a long time because if you don't start bending the curve in the out years, we are hosed."
By supporting Trump, tea party Republicans would also put themselves on the record as being in favor of big increases in certain kinds of government spending.
Tea party Republicans will soon discover that President Trump's budget doesn't really add up. They will be receiving numbers from a Republican administration, which generally is sympathetic to their goals on most major issues, that will contradict their promise to the reddest constituents that they would hold firm on the anti-government cause. Jim DeMint, the former South Carolina senator, said, "America cannot wait any longer before we get serious about balancing the budget."
Trump is putting the Republican Party in a difficult spot at a moment of united government that could easily have turned into a period of triumph. If tea party Republican members of Congress swallow what the President has sent them, they will quickly reveal to their supporters that they are as craven and opportunistic as anyone else in Washington. They will place themselves at risk to be "tea partied" out of office and they will greatly damage their own credibility with the electorate in the coming election cycle.
If they hold to principle, as they did under President Obama, then the Republicans as a party will be facing a dangerous moment. A Republican President, who has shown that he doesn't have much loyalty when it comes to people getting in the way of his success, will be facing off against a huge portion of the congressional Republicans. The Freedom Caucus, with about 32 votes, has the numbers in the House to tie up the administration.
Will Republicans unite and make the most of their control of Congress and the White House? Or will many of them remain true to their small government philosophy and risk war with a White House that wants to reshape Washington?