With Sen. Luján in the hospital after a stroke, Democrats have no Senate majority and can't pass anything without GOP help

• Democratic Sen. Ben Ray Luján's office announced Tuesday he had suffered a stroke.
• His absence means that Democrats' razor-thin Senate majority is gone.

News that Sen. Ben Ray Luján of New Mexico had suffered a stroke shocked Congress Tuesday, with colleagues expressing concern for his welfare and relief when his office announced he was expected to make a full recovery.

But with the duration of his recovery time unknown, his absence also exposed the fragility of the Democratic Party's control of the Senate.

Currently, the Senate is divided 50-50, with Vice President Kamala Harris holding a tie-breaker vote, the narrowest possible way for a party to have control of the chamber.

The filibuster rule, requiring at least 60 votes for many measures, already put many actions beyond the reach of Democrats with Republican help.

But there were other steps, including so-called reconciliation bills devoted to finance and approving nominees to the Supreme Court, which could be done with 50 votes and the tie-breaker.

Without Luján, that can only be done with help from at least one Republican senator.

Justice Stephen Breyer announcement last week that he was retiring from the Supreme Court, meant that President Joe Biden will be able to make the first Supreme Court pick of his presidency.

It was a much-needed boost for Democrats after a string of legislative setbacks, and bad news on issues ranging from the Ukraine crisis to inflation badly dented Biden's poll ratings.

Also on the cards was passing some form of Biden's signature Build Back better bill, a sweeping climate social care and climate change package that has stalled amid the the opposition of Democratic moderate Sen. Joe Manchin.

Democrats had discussed breaking up the bill and passing key parts of the package that Manchin had signaled he could back.

Luján's absence casts doubt over the ability of Democrats to deliver.

CNN projected that if Biden moved according to the timetable he has mapped out, and nominates a new justice by the end of the month, the Senate could still proceed as planned even with Luján out of action for two months.

Having lost his majority for the time being, Sen. Majority Leader Chuck Schumer will only be able to press ahead with bills likely to gather some Republican backing, which could perhaps be found on measures such as extra sanctions for Russia.

Former President Donald Trump may further complicate matters.

Trump has attacked Senate Republicans for any compromises with Democrats, and could perceive Luján's absence as another area where he will push the party to obstruct Biden's party at all costs.