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The Cleric takes Extend Spell and Persistent Spell, then takes a handy little feat from Complete Divine called Divine Metamagic, which lets him spend his turn attempts to apply metamagic feats to his spells (specifically, Persistent Spell).

Next, he has to find a way to get a bunch of turn attempts. Extra Turning does the job nicely, and can be taken multiple times, but in Libris Mortis there is a handy and relatively cheap (7.5K gold) wonderous item called a Rod of Nightstick, which adds 4 extra turn attempts per day. Most Clerics carry anywhere between two and five.

The Cleric then casts Righteous Might, Divine Power, and Divine Favor on himself, using his turn attempts to Persist them. The Cleric now has the following benefits all the time:
+10 Strength
+2 Constitution
A Fighter's Base Attack Bonus
d10 Hit Dice
+2 Natural Armor
DR/Evil
Reach (comes with being Large)
At least a +3 Luck bonus on attack and damage rolls

This is, of course, before the Cleric casts his actual buffs, such as Spiritual Weapon, Greater Magic Weapon, and Magic Vestments. These spells alleviate the need for the Cleric to spend money on magic weapons and armor, which means he can spend more money on Nightsticks, which means he can Persist more spells, as well as a Ring of Counterspelling attuned to Dispel Magic, making his buffs all but impossible to dispel.

In short, the Cleric is better than the Fighter at being a meat shield, and is still a Cleric. He can still heal, scry, cast Save or Die spells, use Wands without a UMD check, and everything else Cleric-y. With a minimal feat investment, the Cleric has 100% eclipsed the fighter.

The sad part of this is that the Cleric barely had to dip outside of the core rules to do it. All the spells mentioned above are in the Player's Handbook. All it took for the Cleric to be able to outfight the fighter was three feats (two of them Core) and a single magic item (albeit purchased multiple times).

Fighters are useless.

To be fair, the Cleric without Divine Metamagic is still better than the fighter, he just has to work harder at it. He'll just grab a large number of Wands of Cure Light Wounds, spend all of his spell slots on buff / attack spells, use Extend Spell for all his buffs, and still be totally effing metal. Or, he'll just boost his caster level a ton and make the most out of Holy Word. The main point was that the vast majority of Cleric cheese is available right there in the PHB1, and for the fighter to even compete he needs to dip outside core and make use of the splatbooks.

The Cleric and Druid need to be kept on a tight leash in order to bring them in line. Houseruled banning of key feats is 100% necessary. Read as written, using the rules right there in the core rulebook, the Cleric and Druid are just plain better. Give the Cleric or the Druid the same options you're giving the fighter in terms of what he can and can't use, and he'll punish you for it twelve times over.