To most Americans, the weeklong government shutdown "came out of nowhere," say Sheryl Gay Stolberg and Mike McIntire in The New York Times. But interviews with influential conservative and an examination of tax and campaign finance records shows that this confrontation is the outgrowth of a long-running effort to undo ObamaCare "waged by a galaxy of conservative groups with more money, organized tactics, and interconnections than is commonly known."

Freedom Partners, a tax-exempt group tied to the billionaire brothers Charles and David Koch, is one of the primary bankrollers of the defund effort, doling out more than $200 million last year alone to fight ObamaCare. More than half of that money went to the Center to Protect Patient Rights, which then parceled out much of it to other groups.

The defund or repeal effort dates back to soon after ObamaCare was passed in 2010, but the current push reportedly started in February. "Give the Tea Party credit," says Molly Ball at The Atlantic. "Their grassroots tactics worked."

With a government shutdown ongoing and a potentially calamitous debt-ceiling brawl on deck, here's a closer look at some of the dates that led us to this point:

March 23, 2010
President Obama signs the Patient Protection and Affordable Care Act, commonly known as ObamaCare.

June 28, 2012
The Supreme Court upholds most parts of the law, but strikes down the requirement that individual states have to accept an expanded Medicaid program.

November 6, 2012
Obama is re-elected, defeating Republican Mitt Romney. Democrats keep control of the Senate. Republicans keep control of the House.

November 8, 2012
House Speaker John Boehner (R) tells ABC News' Diane Sawyer: "It's pretty clear that the president was re-elected, ObamaCare is the law of the land." His spokesman, Kevin Smith, later qualifies Boehner's statement: "While ObamaCare is the law of the land... Speaker Boehner and House Republicans remain committed to repealing the law, and he said in the interview it would be on the table."

February 13, 2013
The Conservative Action Project, a coalition of activists and organizations led by Reagan-era Attorney General Edwin Meese III, meets in Washington and comes up with a "blueprint to defunding ObamaCare." The original plan is to attach a defunding amendment to a continuing resolution (CR) to fund the government after March 27. "Although the Obama administration and others will argue the CR is not the appropriate legislative vehicle to defund ObamaCare, it is easily done through a series of appropriation riders," the blueprint states. The 46 signatories encompass a broad array of fiscal and social conservative groups, including the heads of the Club for Growth, FreedomWorks, Heritage Action, Tea Party Patriots, and the Traditional Values Coalition.

July 11
Rep. Tom Graves (R-Ga.) introduces the self-explanatory Defund ObamaCare Act of 2013.

Representatives from Heritage Action, ForAmerica, Tea Party Patriots, the Family Research Council, and other conservative groups meet with Sens. Mike Lee (R-Utah), Ted Cruz (R-Texas), and Marco Rubio (R-Fla.) to come up with a plan to force Republican leaders in Congress to insist on defunding ObamaCare as a condition for funding the government.

July 23
Heritage Action announces that it will keep of track of how individual representatives vote on Graves' "defund" ObamaCare bill, making it a "key" vote that will affect Republicans' congressional scorecards that Heritage Action puts together at the end of the year. "Representatives should co-sponsor the Defund ObamaCare Act AND tie it to a 'must-pass' bill, such as the year-end funding bill," Heritage Action says.

July 24
Heritage Action strongly advises Republicans to sign a letter being circulated by first-term Rep. Mark Meadows (R-N.C.) that urges Boehner to take whatever steps necessary to defend ObamaCare entirely, up to and including attaching the demand to a congressional resolution to fund the government.

August 19
Heritage Action starts a 10-day "Defund ObamaCare Town Hall Tour," featuring Cruz, his father, Rafael Cruz, and Heritage Foundation President Jim DeMint. Hundreds attend every stop of the tour.

August 21
Meadows sends his letter to Boehner with 79 fellow Republicans as signatories. Heritage Action runs internet ads in the districts of 100 House Republicans who failed to sign Meadows' letter. "They've been hugely influential," says Cook Political Report's David Wasserman. "When else in our history has a freshman member of Congress from North Carolina been able to round up a gang of 80 that's essentially ground the government to a halt?"

September 20
The House votes to strip financing for ObamaCare, for about the 40th time, attaching it to the continuing resolution.

September 24-25
Cruz stages his 21-hour speech on the Senate floor, making sure that the effort to defund ObamaCare gets plenty of media attention.

September 27
The Senate removes the amendment to defund ObamaCare and sends a "clean" CR back to the House.

September 29
The House approves a CR that delays ObamaCare for a year, repeals a medical device tax, and allows employers to opt out of providing contraception to its employees.

September 30
The Senate strips out the House add-ons and sends back a clean CR. The House sends back a bill delaying the individual mandate to the Senate, which promptly returns another clean CR.

October 1
The government begins to shut down. At 1 a.m., the House sends the Senate back its earlier version, with the one-year delay of the individual mandate, plus a request to form a conference committee to negotiate a bill that can pass both chambers. The Senate convenes and tables the House's motion.

Sources: The Atlantic, NBC News, New York Times (2), Slate, Politico