The Big Conversation

Julián Castro and Dan Patrick square off this evening in a San Antonio television studio for their long-awaited debate over immigration. We will livestream the 6 p.m. event, which is moderated by the Tribune's Evan Smith. In the meantime, here are some things to watch for tonight:

• Tone: Patrick is the candidate with all the momentum in the GOP runoff contest for lieutenant governor against the incumbent David Dewhurst. His "jarring message" on illegal immigration — to use the phrase from the San Antonio Express-News' John W. Gonzalez — is one of the reasons why. Will he moderate his language in a forum taking place in a Univision studio that will be shown on Spanish-language affiliates across the state? His success with the GOP electorate raises the follow-up question, why would he change anything?

• Whither the Host: Castro, the San Antonio mayor, has the hometown advantage. But unlike Patrick, he's not running for anything currently. The Express-News' Gonzalez notes that Castro isn't being talked about for a White House run in 2016. So what's in it for him? This is the man who had the keynote slot in the last Democratic national convention, so it's hard to see how much more this event will raise his profile.

• The Missing Man: Conspicuous by his absence from this evening's forum is Dewhurst. Already fighting the widespread perception that momentum has shifted decisively toward Patrick, Dewhurst will be watching along with the rest of the general public tonight. "It's the difference between rising and fading. Dan is rising and Dave is fading," said Republican strategist Matt Mackowiak, as reported by the Houston Chronicle's David Saleh Rauf.

The Day Ahead

• U.S. Sen. Marco Rubio, R-Fla., makes a couple of stops in Texas today, beginning in San Antonio, where he takes part in a conversation with the Tribune's Evan Smith at noon at the Embassy Suites Riverwalk. Rubio then heads up I-35 to Austin, where he will make an address at 4 p.m. at the Blanton Museum of Art Auditorium on “Moral Clarity and America's Role in the World.”

• Democratic gubernatorial candidate Wendy Davis addresses the Texas Retired Teachers Association Annual Convention in Dallas at 11 a.m.

• The Senate Higher Education Committee holds an interim hearing at 9 a.m. in the Capitol Extension to take a look at progress on the Closing the Gaps initiative. (agenda)

• The Senate Veteran Affairs and Military Installations Committee holds an interim hearing at noon in the Capitol Extension on workforce issues for veterans and service members. (agenda)

• The House Human Services Committee holds an interim hearing at 9 a.m. in the Capitol Extension to look at the redesign of foster care in the state and the adoption process. (agenda)

Today in the Trib

Ahead of November, Parties Hone Women's Health Messages: "With last session's divisive abortion debate as a backdrop, Democrats are getting help from the newly created Planned Parenthood Texas Votes Action Fund. Republicans, meanwhile, have their own group to tackle women's issues."

Calculator Directive for 8th-Graders Draws Concerns: "Starting in the 2014-15 school year, eighth-graders in Texas public schools will be required to have graphing calculators or tablets for STAAR assessments. Some poorer school districts are concerned that the mandate ignores fiscal challenges they're already facing."

Analysis: For Texas Libertarians, "Small D" Democracy: "Not all political candidates are chosen in primary elections. Some get on the November ballot with the votes of fewer people than you might see at a local Tea Party rally."

Committee to Examine Effectiveness of Foster Care Redesign: "Supporters of a foster care redesign are hopeful that the program will improve the quality of care for children. But some advocates are raising questions about the program's oversight."

Must-Read

Grand jury to look at Perry veto threat, Houston Chronicle

Fire marshal proposes tougher rules to prevent another West, The Dallas Morning News

House panel refers report on UT Regent Wallace L. Hall Jr. to prosecutors, Austin American-Statesman

Wendy Davis says her top priority as a senator has been to serve Texans, not her clients, The Dallas Morning News

Ted Cruz Is Beating Rand Paul in the Tea Party Primary, The Atlantic

Texas senators voice concern over poor high school test scores, The Dallas Morning News

Man gets 7 years for torching Wendy Davis’ office, Fort Worth Star-Telegram

Former sheriff Lupe Treviño admits to money laundering, McAllen Monitor

Quote to Note

"Simply put, this would not happen in Texas. I implore the Tran Family: just meet with us. Let us tell you what is possible by moving your operations to Texas. You will not be disappointed."

— State Rep. Jason Villalba, R-Dallas, continuing his increasingly lonely quest to get the makers of Sriracha to leave California for North Texas

Trib Events for the Calendar

• A Conversation With Mike Collier, Candidate for State Comptroller at the Austin Club, 4/17

• Slate's Live Political Gabfest in Austin at Scholz Garten, 4/23

• A Panel Discussion on Keeping the Lights on in Texas at St. Mary's University in San Antonio, 4/29

• The Texas Tribune Festival On the Road presents a one-day symposium on STEM Education at UT-Dallas, 5/5

• A Conversation With Rep. Dan Branch, Candidate for Attorney General at the Austin Club, 5/8

• A Conversation with U.S. Rep. Mike Conaway at Midland College in Midland, 5/13

• A Conversation With Steve Patterson, UT Men's Athletic Director at the Austin Club, 5/15

• A Conversation With Sen. Glenn Hegar, Candidate for State Comptroller at the Austin Club, 5/29

• Save the date for the 2014 Texas Tribune Festival: 9/19-9/21