Senate Democrats are apparently pushing ahead with their proposal to cripple President Donald Trump’s presidency by blocking his campaign promise to build a secure border wall between the United States and Mexico’s drug runners, criminals and illegal immigrants.

The threat, leaked in early March, was made clear in a letter from Democratic leaders in the Senate, who said they were “concerned with reports that there may be an effort to include funding for a very expensive border wall” in a special budget planned for early 2017.

“We believe it would be inappropriate to insist on the inclusion of such funding in a must-pass appropriations bill that is needed for the Republican majority in control of the Congress to avert a government shutdown so early in President Trump’s Administration,” said the letter, which was signed by the Democrats’ Senate leader, Sen. Chuck Schumer, and other Democratic leaders, including Democrat Sens. Dick Durbin, Sen. Patty Murray, Sen. Debbie Stabenow and Sen. Patrick Leahy.

The letter was shared with a variety of media outlets before it was sent to the GOP leaders, including Majority Leader Sen. Mitch McConnnell.

The letter also sought to protect other progressive priorities from Trump’s budget cutting and policy changes, by saying Democrats would oppose any funding changes that would:

roll back protections for our veterans, environment, consumers, and workers and prohibit funds for critical healthcare services for women through Planned Parenthood. We strongly oppose the inclusion of such riders in any of the must-pass appropriations bills that fund the government.

The Democrats have some leverage over the GOP in the Senate because they can block legislation unless eight of the 48 Democratic Senators vote with the GOP to end a debate and schedule voting on a pending bill.

In turn, the GOP has enormous leverage on Democrats, because they can blame the Democrats for blocking a federal budget and for obstructing an elected president.

The GOP is already in a very good position to add several additional Senate seats in the 2018 elections to their 52-seat majority. For example, 10 Democrats Senators in states that voted for Trump in 2016 have to face the voters in November 2018, while only one GOP Senator is facing election in a state won by Hillary Clinton. If the GOP gains only five seats in 2018, it will have just three votes short of a 60-vote supermajority in the Senate.

Numerous polls show that strong majorities of Americans want to reduce the flow of drugs, preserve U.S. jobs for Americans and also want Congress to pass laws that help Americans. In 2006, Congress passed a law authorizing — but not funding — the construction of a border wall.

Also, Schumer’s last big strategic decision — his championship of the cheap-labor “Gang of Eight” amnesty in 2013 — backfired spectacularly once GOP politicians recognized the business-funded pro-amnesty polls were hiding the public’s strong anti-amnesty attitudes. Schumer believed the flawed pro-amnesty polls, so Democrats lost nine seats in the 2014 election, the GOP’s base backed pro-American Donald Trump in the 2016 primaries, and Democratic voters dismantled their own party’s “Blue Wall” in the Midwest states on November 8, making Schumer the second-biggest loser of the night.