Iowa in Recent Presidential Elections

Iowa population by census (source). Notice how the number has no changed much over he last fifty years.  The shifts in voting patterns can't be chalked up to new arrivals or drastic demographic shifts.

1960	2,757,537		5.2%
1970	2,824,376		2.4%
1980	2,913,808		3.2%
1990	2,776,755		−4.7%
2000	2,926,324		5.4%
2010	3,046,355		4.1%

2012 (source)

	Democratic	Barack Obama	Joe Biden	822,544	51.99%	6
	Republican	Mitt Romney	Paul Ryan	730,617	46.18%	0
	Libertarian	Gary Johnson	Jim Gray	12,926	0.82%	0

2008

2008 (source)

	Democratic	Barack Obama	828,940	53.93%	7
	Republican	John McCain	682,379	44.39%	0
	Peace and Freedom	Ralph Nader	8,014	0.52%	0
	N/A	Write-ins	6,737	0.44%	0
	Libertarian	Bob Barr	4,590	0.30%	0

 

2004

2004 (source)

	Republican	George W. Bush	Richard Cheney	751,957	49.90%	7
	Democratic	John Kerry	John Edwards	741,898	49.23%	0
	Independent	Ralph Nader	Peter Camejo	5,973	0.40%	0
	Libertarian	Michael Badnarik	Richard Campagna	2,992	0.20%	0

2000

2000 (source)

	Democratic	Al Gore	638,517	48.54%	7
	Republican	George W. Bush	634,373	48.22%	0
	Green	Ralph Nader	29,374	2.23%	0
	Reform	Pat Buchanan	5,731	0.44%	0
	Libertarian	Harry Browne	3,209	0.24%	0

1996

1996 (source)

	Democratic	Bill Clinton (incumbent)	Al Gore	620,258	50.26%	7
	Republican	Robert Dole	Jack Kemp	492,644	39.92%	0
	Reform	Ross Perot	James Campbell	105,159	8.52%	0
	Green	Ralph Nader	Anne Goeke[1][3]	6,550	0.53%	0

1992

1992 (source)

	Democratic	Bill Clinton	586,353	43.29%	7
	Republican	George H.W. Bush	504,891	37.27%	0
	Independent	Ross Perot	253,468	18.71%	0
	Natural Law	Dr. John Hagelin	3,079	0.23%	0

1988

1988 (source)

	Democratic	Michael Dukakis	670,557	54.71%	8
	Republican	George H.W. Bush	545,355	44.50%	0
	Independent	Lyndon LaRouche	3,526	0.29%	0
	Libertarian	Ron Paul	2,494	0.20%	0

1984

1984 (source)

	Republican	Ronald Reagan	703,088	53.27%	8
	Democratic	Walter Mondale	605,620	45.89%	0
	Independent	Lyndon LaRouche	6,248	0.47%	0
	Libertarian	David Bergland	1,844	0.14%	0

1980 

(source)

R	Ronald Reagan	George Bush	Republican	676,026	51.31%	8
D	James Carter	Walter Mondale	Democrat	508,672	38.60%	0
I	John Anderson	Patrick Lucey	Nom. Petition	115,633	8.78%	0

1976 

(source)

R	Gerald Ford	Robert Dole	Republican	632,863	49.47%	8
D	James Carter	Walter Mondale	Democrat	619,931	48.46%	0
I	Eugene McCarthy	-	Nom. Petition	20,051	1.57%

1972 

(source)

R	Richard Nixon	Spiro Agnew	Republican	706,207	57.61%	8
D	George McGovern	R. Sargent Shriver	Democrat	496,206	40.48%	0
I	John Schmitz	Thomas Anderson	American Ind.	22,056	1.80%	0

1968 

 (source)

R	Richard Nixon	Spiro Agnew	Republican	619,106	53.01%	9
D	Hubert Humphrey	Edmund Muskie	Democrat	476,699	40.82%	0
I	George Wallace	S. Marvin Griffin	American Ind.	66,422	5.69%	0

1964

 (source)

D	Lyndon Johnson	Hubert Humphrey	Democrat	733,030	61.88%	9
R	Barry Goldwater	William Miller	Republican	449,148	37.92%	0

1960

(source)

R	Richard Nixon	Henry Lodge	Republican	722,381	56.71%	10
D	John Kennedy	Lyndon Johnson	Democrat	550,565	43.22%	0