Sen. Ted Cruz (R-Tex.) (Jim Watson/AFP/Getty Images)

The eyes of the political world will once again turn to South Carolina on Friday, where state Democrats and Republicans plan to hear from two potential 2016 presidential candidates -- and one who might run a few years later.

Vice President Biden (Reuters)

Vice President Biden, who hasn't ruled out running to succeed his boss, plans to speak Friday night at the annual Jefferson-Jackson Dinner, where he'll be joined by his old Senate friend Fritz Hollings and Rep. James Clyburn (D-S.C.), among other party officials. After the dinner, the party faithful will decamp to Clyburn's annual Fish Fry, a legendary and must-attend event for anyone harboring serious presidential ambitions.

At the same hour just a few blocks away at the state fairgrounds, Sen. Ted Cruz (R-Tex.) will headline the South Carolina Republican Party Silver Elephant Dinner, which this year will pay tribute to former South Carolina senator Jim DeMint, who's now leading the Heritage Foundation. The invite for Cruz is significant, as friends of the senator said this week that he’s mulling a possible presidential bid at the behest of enthusiastic supporters.

Sen. Lindsey Graham (R-S.C.) (AP)

The state's top GOP stars, Gov. Nikki Haley and Sens. Lindsey Graham (R-S.C.) and Tim Scott (R-S.C.), also plan to speak at the dinner. Former governor and congressional hopeful Mark Sanford will not be attending, as he plans to campaign in southern parts of the state ahead of Tuesday's special House election.

Even though Election Day 2016 is more than three years away, both dinners promise to draw the national political press (including this reporter) to South Carolina, because any speech Biden and Cruz (and several other potential candidates) give in an early primary state is worth watching unless, or until, they rule out running for president. The two speeches are seen as so significant that C-SPAN is using them to launch its "Road to the White House 2016" series.

So, why are Biden and Cruz both in Columbia on the same night? Because of state law.

South Carolina requires the two political parties to hold their annual conventions each year in May to elect new officers and take care of housekeeping tasks. Those formal meetings are planned for Saturday.

Regardless of the timing, "I think that South Carolina in January through December of any year -- whether it's three years out or four years out or eight years out -- is always the center of the political universe," said Alex Stroman, executive director and spokesman for the South Carolina GOP. "We're used to it, and we love it."

At those Saturday conventions, Republicans are to hear again from Haley and Graham. The senator faces a reelection campaign next year, and given his recent work on immigration -- and his initial support for debating gun-control -- observers will be watching to see how the party faithful respond to his remarks.

Democrats have invited Rep. Joaquin Castro (D-Tex.) to give the keynote address at their annual convention. His brother, San Antonio Mayor Julian Castro (D), gave the keynote at last year's Democratic National Convention -- and each is also seen as a future presidential contender.

For updates from South Carolina tonight and this weekend, follow Ed O'Keefe on Twitter: @edatpost