The Senate’s immigration debate ended before it began because Democrats must have it continue. Democrats face just such contradiction from internal and external pressure to keep the immigration issue alive through at least this November. More importantly, agreement with the president on immigration now risks their losing this issue forever.

The left has made immigration a liberal litmus test. This makes for severe internal pressure for a Democratic Party receiving overwhelming liberal support. As evidence, the left goaded Democrats into a three-day government shutdown over DACA earlier this year.

Further aggravating this inherent internal pressure is Democrats’ ending that shutdown without a substantive DACA win. Recently they compounded that omission by agreeing to a two-year funding deal also containing no victory on DACA. Having let “must-pass” legislation go by, Democrats need a place to show a stand: A broad immigration debate fit perfectly.

It particularly did because there is equally intense internal pressure to avoid a broad immigration debate guaranteed to produce votes that will split off red state Democrats. The last thing Democrats need is to show disunity on this issue to the left.

Democrats’ external pressure is equally intense. President Trump’s polling numbers have been improving. Simply counting on his unpopularity may not be enough in November.

Tax reform also gave him a signature win with the conservative and Republican bases. Prior to this, neither of those could be counted on. Now Democrats cannot be so sure.

The economy’s increasing strength also threatens to draw voters from outside Republicans and the right. Each day shows another company giving bonuses attributed to tax reform. Paychecks have also begun arriving showing a smaller tax bite.

As the economy continues to strengthen, expect wages to grow too. Finally, the psychological “wealth effect” should not be discounted; it is certain to give many voters more positive financial outlooks that will likely have a political component.

With “money issues” now a win for Republicans, Democrats need social issues as a block. Immigration again fills the bill.

If Democrats agree to an immigration deal with President Trump and Republicans, it removes this as a partisan issue. This is especially true if it contains elements — such as increased border security — their opponents want. By agreeing, they will effectively “bless” these as nonpartisan, and even worse for the left, “acceptable.”

On the other side, allowing Republicans to have a bill they can support — the definition of compromise and real debate — “absolves” Republicans and President Trump with America’s majority. Such an outcome would make the right look reasonable for raising them and the left unreasonable for having blocked them so long.

Democrats’ own public projections for November’s election also undercut their ability to reach agreement now. If they expect such a win, then why have the immigration debate now?

If they truly believe their projections, then Democrat numbers will be bigger next year and their leverage on immigration therefore greater. Even if they do not believe them, they are stuck because the left does, seeing them as further reason to not hold this debate now.

The left and Democrats’ interest in this issue also extends past this November. In 2016, Trump trounced (57 percent to 37 percent) Clinton among White voters, who made up 71 percent of voters. However, he lost heavily among Black voters (8 percent to 89 percent and made up 12 percent of voters) but not nearly as much among Latino voters (28 percent to 66 percent and made up 11 percent of voters).

As the left and Democrats recall: Trump won despite low support among Blacks and Latinos. With no other big voting blocs out there, Democrats cannot afford long-term to let President Trump and Republicans further into the growing Hispanic voting group.

Instead, immigration and DACA serve as the left’s wedge issue to keep President Trump and Republicans apart and ideally — without a bipartisan compromise being struck — cutting into moderate voters who might be economically attracted to the right.

For now, expect the immigration debate to be ever in need of beginning, but never in reality ending. The left simply cannot afford resolution, let alone a bipartisan one.