WASHINGTON — From the nation’s Capitol to the Texas Capitol, the scuttlebutt was that Democratic U.S. Rep. Joaquin Castro would announce within days — if not hours — his campaign for U.S. Senate.

That was four weeks ago.

Back then, practically everyone in politics assumed his challenge to U.S. Sen. John Cornyn was inevitable. More than a handful of political allies rushed to publicly and privately add their political clout to his potential campaign, with the belief that a long-pined-for statewide Castro campaign would be unstoppable.

Now, more than a dozen Texas and national Democrats say they are increasingly skeptical that Castro will run at all.

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Those allies are baffled and frustrated with the the lack of political clarity coming from the Castro camp, especially given that veteran M.J. Hegar announced her own run for the Democratic nomination earlier this week.

One of Castro's closest friends in the Congressional delegation, Filemon Vela, went so far as joining a draft Castro campaign. This is the second time Vela has thrown his support behind his colleague. Castro similarly spent the spring of 2017 publicly mulling a run against Ted Cruz, the state's junior senator, only to return his focus on the U.S. House. Vela texted the Tribune on Wednesday that he is "exasperated with the indecision" — an oft-repeated sentiment that a half-dozen state and national Democrats expressed privately.

But an announcement is nigh. Castro will announce his decision by Wednesday, according to his top political aide, Matthew Jones.

Yet the decision will follow weeks of frustration that dates to March and has come amid a succession of mixed signals from the four-term congressman.

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The party's last Senate nominee, former U.S. Rep. Beto O'Rourke, announced he would forgo another U.S. Senate run next year in lieu of a presidential campaign. The overriding sense was, given that Castro took a pass two years ago, 2020 was his chance to run and his nomination to lose.

At the same time, Democrats of large and small stature began publicly airing their Senate ambitions. One of those Texans was Hegar, who proved to be a fundraising powerhouse even as an unsuccessful U.S. House candidate last cycle.

And in that race she had the support of the fundraising juggernaut EMILY's List, a group that works to elect Democratic women who support abortion rights. While EMILY's List has yet to endorse Hegar, the organization's leaders have made plain that they are seriously considering spending money against Cornyn.

Several news reports in mid-March stated that Castro's announcement was imminent. Politicians across the state began to organize around the notion of Castro running for Senate, trying to avoid holding major events on speculated dates when he might announce. Up in Washington, House Democratic leaders were sizing up potential candidates who might run to succeed him in his San Antonio-based Congressional seat.

And then, according to nearly a dozen state and national Democrats interviewed for this story, Castro went quiet.

Patience wore thin in mid-April when Castro filed his quarterly campaign finance reports.

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U.S. House members have a unique advantage when running for Senate: They can raise money for their House campaigns without officially announcing for the upper chamber. Once he or she makes those Senate intentions known, the member can then transfer the House money to Senate accounts. Oftentimes, House members will put out the message they are running in order to raise their profiles and coffers, only to pull back.

Castro’s filing showed he raised $36,000, a sum that could barely cover the cost of a statewide poll in Texas. In comparison, then-U.S. Rep. Kyrsten Sinema of Arizona raised $677,000 in the same window two years ago as she geared up for her eventual Senate run.

But it is more complicated than that, Jones told the Tribune.

Castro's twin brother, Julián Castro, launched his own presidential campaign in January.

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"Joaquin spent much of the first quarter overseeing the launch of his brother's presidential campaign," he said. "That's a commitment he wanted to keep."

Furthermore, Jones pointed out, Joaquin Castro has been at the center of legislative pushback against President Donald Trump. Joaquin Castro led his party in rebuking Trump's emergency order to build a wall on the Mexican border. U.S. House Speaker Nancy Pelosi went out of her way on several occasions during that controversy to credit his foresight on the issue.

As chairman of the powerful Congressional Hispanic Caucus, Joaquin Castro has a future in the U.S. House, should he stay. But the Senate deliberations have diverted from opportunities there, too. While he's been enmeshed in Senate political calculations, younger House members are positioning to run for leadership next year.

In Texas, the political class is mostly just flat confused about his intentions. Just as most Democratic insiders began to believe he would not run for Senate, Joaquin Castro appeared in Austin last week in a news conference that seemed timed to counter one that Cornyn held with other state leaders. Joaquin Castro took several shots at the incumbent.

"The U.S. senators right now in Washington are too afraid of President Trump ... to stand up for Texas," he said. "It's clear that we need stronger leadership in this state to stand up when the president or anyone else tries to mess with Texas."

Should Joaquin Castro decide to make a Senate run, it will be the first time in recent memory that the state will host a truly competitive primary for the U.S. Senate Democratic nomination.

Besides Hegar, Houston City Councilwoman Amanda Edwards is still considering a run. Two Dallas sources tell the Tribune that state Sen. Royce West has had recent conversations about his own potential run. And businesswoman Sema Hernandez is running again, after giving O'Rourke a run for his money in several Rio Grande Valley counties.

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This new dance — how to handle intraparty positioning and potential primary fights — is a high-class problem Texas Democrats have not had to handle in decades. Before O'Rourke nearly toppled Cruz last year, the Democratic nomination for U.S. Senate was uniformly viewed as a ticket to being a historical footnote and sacrificial lamb.

And these deliberations do not happen in a Texas vacuum. The Democrats' Senate campaign arm has a history of picking favorites and often pushing candidates out of primaries. The Austin American-Statesman reported Friday that Senate Minority Leader Charles Schumer is not keen on Joaquin Castro.

"I think that probably the era of uncontested primaries in both parties in Texas is over," Joaquin Castro said last week.

Whether this primary will include him remains the operative question in Texas politics.

Patrick Svitek contributed to this report.