The OED suggests that bloviate is probably a conjoining (or collocation, as eytmologists prefer) of the verb blow and the affix -viate (as in e.g. deviate., abbreviate), where blow is the "motion or action of the wind, or of an aerial current, as in 'it blows hard,' 'it blew a gale, a hurricane,' to blow great guns: to blow a violent gale; to blow up; to rise, increase in force of blowing."
Within the word "bloviate," blow becomes a root signifying nothing more than an empty conceptual or emotional space that is aflow with currents, each current devoid of anything substantial, i.e., of words in syntax making meaning.
"Occasionally a candidate makes some great pronouncement or
drastic shift of position in such an oration, but more often
he merely talks, or, as [Warren G.] Harding [picture at right] put it, ‘bloviates’, being concerned more with the political effect of his remarks than with their meaning."--1957 Amer. Hist. Rev. 62 1014.
Chávez seems enamored of the sound of his own voice, and he has an unpopular habit of taking over Venezuela's TV and radio stations to bloviate about his reforms.-- 2002 Mother Jones May-June 82/2.
--Note: definition, etymology, and quotations above come from OED Online.
BLOVIATE (ab ovo):
The story is that President Warren G. Harding, a notoriously flawed public speaker, coined the words normalcy and bloviate. Though he simply revived an erstwhile dying version of the word "normality" (no small feat), he probably did invent the devilishly clever word "bloviate." Those distinctions aside, Harding's public career is remembered best for his bad speeches, oversight (in both senses) of rampant corruption, and well-known philandering.
W. G. HARDING AS INSPIRATION
FOR A POEM BY JOHN ASHBURY:
John Ashbery uses "bloviate" in his poem "Qualm" about Warren G. Harding. The poem speaks of Harding's final moments in the arms of his long-suffering wife, following an arduous train trip to Alaska. Here are the opening stanzas:
Warren G. Harding invented the word "normalcy,"
Also the lesser-known "bloviate," meaning, one imagines,
To spout, to spew aimless verbiage. He never wanted to be President.
The "Ohio Gang" made him. He died in the Palace
Hotel in San Francisco, coming back from Alaska,
As his wife was reading to him, about him,
From The Saturday Evening Post. Poor Warren. He wasn't a bad egg,
Just weak. He loved women and Ohio
--Yahoo Education page (http://education.yahoo.com/reference/
AS WORDSMITH AND
In his thoroughly encompassing scorching style, Social Critic and etymologist H. L. Mencken had this to say about Harding's oratorical infelicities [in- = "not-" + felix = "happy"]:
That is to say, he [Warren G. Harding] writes the worst English that I have ever encountered. It reminds me of a string of wet sponges; it reminds me of tattered washing on the line; it reminds me of stale bean soup, of college yells, of dogs barking idiotically through endless nights. It is so bad that a sort of grandeur creeps into it. It drags itself out of the dark abysm (I was about to write abscess!) of pish, and crawls insanely up the topmost pinnacle of posh. It is rumble and bumble. It is flap and doodle. It is balder and dash.--http://education.yahoo.com/reference/quotations
"HOW TO BLOVIATE WITH
ONE'S FOOT IN ONE'S MOUTH"
By BLOGGIN' JOHN
Back in April of 1998, I had already collected a fair number of word-books, thesauri, and dictionaries. But I did not have the Random House Webster's College Dictionary (keep this in mind). Being interested in the word bloviate, I checked all of my main stream dictionaries (mostly, from the houses of Merriam-Webster and American Heritage), but could find nary a reference to the word. Blithely assuming (but without checking) that Random House had also ignored the word, I sent a smirky question about the apparently lost and wandering bloviate to Jesse Sheidlower, who at the time--before his present work as Editor-at-Large for the Oxford English Dictionary--was working for Random House as the keeper of the interactive website "Jesse's Word of the Day."
JOHN'S QUESTION & JESSE'S ANSWER
April 10, 1998
John . . . writes: The word "bloviate" is now more evident on the Web (put it into a search engine sometime), in discussion groups (check out NYT's "Etymology"), and in specialty dictionaries than it is in mainstream lexicons. How much of a current presence does a word need to appear in a modern dictionary?
[Jesse Sheidlower answers:] What, like the Random House Webster's College Dictionary, which has an entry for bloviate with the definition 'to speak pompously'? It doesn't need any more currency, since the word has quite a bit and it's already in this dictionary. If you're using one of those other dictionaries, with generally poorer coverage of current vocabulary, well, that I can't help you with.
There has been quite a vogue in recent years for bloviate, particularly in political discourse. Rush Limbaugh, according to one source, "chortles, crows, bloviates and denounces; but there is always an undercurrent of self-deprecating humor that makes his elephantine egotism bearable." Uh-huh. "In Washington," another source tells us, men "talk too much. Everywhere you look, there are men talking. It's like a giant Bloviation Bee."
Bloviate is not, however, a recent creation. It was apparently coined in the mid-nineteenth century and was found in slang dictionaries by the end of the nineteenth century. Some of the early examples still strike the modern ear as contemporary sounding; the Literary Digest in 1909 derided a proposal to create a state of Los Angeles, "which would rid California of a maximum of bluster and bloviation and a minimum of territory." Hmm, still sounds viable. But bloviate was chiefly popularized by President Warren G. Harding in the early 1920s, and current examples often mention him as the inspiration for the word.
The word bloviate is, of course, an Americanism. It is a pseudo-Latin alteration of blow, in its slang sense 'to boast', also the inspiration for the early-nineteenth-century blowhard. This type of word-formation--adding Latinate affixes to English words--was popular at the time; some of the words that still have some currency is [Sic] absquatulate  'to run away; flee' from abscond and squat, and obfusticated, for 'confused; obfuscated.'
--Words @ Random, "The Mavin's Word of the Day"(http://www.randomhouse.com/words).
 For more about absquatulate, see Words Worthy's posting on it for February 14, 2007.
"Thank You!" to Sean for noting that on every FoxNews broadcast of the eponymous "O'Reilly Factor," host Bill O'Reilly* uses the word bloviate as one of his signature words.
*Aka "Billo" to his vexatious time-slot competitor, Kieth Olbermann, at MSNBC's "Countdown."
A PROVERB FOR BLOVIATION-AFFLICTED SOULS
Blessed is the man who, having nothing to say,
abstains from giving worldly evidence of the fact.
George Eliot (1819-1880)